diff --git a/doc/src/Howto_client_server.txt b/doc/src/Howto_client_server.txt
index ce9bbc07638584ffbfc64e4ac2e5ed29e95b56c9..714c23f0669eed55eaa15e31f100d117e5e2448c 100644
--- a/doc/src/Howto_client_server.txt
+++ b/doc/src/Howto_client_server.txt
@@ -119,12 +119,13 @@ For message exchange in {mpi/one} mode:
 
 Launch both codes in a single mpirun command:
 
-mpirun -np 2 lmp_mpi -mpi 2 -in in.message.client -log log.client : -np 4 lmp_mpi -mpi 2 -in in.message.server -log log.server
+mpirun -np 2 lmp_mpi -mpicolor 0 -in in.message.client -log log.client : -np 4 lmp_mpi -mpicolor 1 -in in.message.server -log log.server
 
 The two -np values determine how many procs the client and the server
 run on.
 
-A LAMMPS executable run in this manner must use the -mpi P
-command-line option as their first option, where P is the number of
-processors the first code in the mpirun command (client or server) is
-running on.
+A LAMMPS executable run in this manner must use the -mpicolor color
+command-line option as their its option, where color is an integer
+label that will be used to distinguish one executable from another in
+the multiple executables that the mpirun command launches.  In this
+example the client was colored with a 0, and the server with a 1.
diff --git a/doc/src/Run_options.txt b/doc/src/Run_options.txt
index b58aaa16e10c5cc983d99548e47cdadc6100ca8c..27f436ed55e4825886789259778e22f0b51819ce 100644
--- a/doc/src/Run_options.txt
+++ b/doc/src/Run_options.txt
@@ -18,7 +18,7 @@ letter abbreviation can be used:
 "-i or -in"_#file
 "-k or -kokkos"_#run-kokkos
 "-l or -log"_#log
-"-m or -mpi"_#mpi
+"-m or -mpicolor"_#mpicolor
 "-nc or -nocite"_#nocite
 "-pk or -package"_#package
 "-p or -partition"_#partition
@@ -176,7 +176,7 @@ Option -plog will override the name of the partition log files file.N.
 
 :line
 
-[-mpi] color :link(mpi)
+[-mpicolor] color :link(mpi)
 
 If used, this must be the first command-line argument after the LAMMPS
 executable name.  It is only used when LAMMPS is launched by an mpirun
diff --git a/doc/src/message.txt b/doc/src/message.txt
index 6c84f3135c58185d0854b2728a0a15d78a2015a4..cca1a5b369fd72d8ffe6eb9db99698c9a39c5e43 100644
--- a/doc/src/message.txt
+++ b/doc/src/message.txt
@@ -105,12 +105,12 @@ mode on a parallel machine, e.g. a cluster with many nodes.
 For mode {mpi/one}, the 2 codes communicate via MPI and are launched
 by the same mpirun command, e.g. with this syntax for OpenMPI:
 
-mpirun -np 2 lmp_mpi -mpi 2 -in in.client -log log.client : -np 4 othercode args  # LAMMPS is client
-mpirun -np 2 othercode args : -np 4 lmp_mpi -mpi 2 -in in.server  # LAMMPS is server :pre
+mpirun -np 2 lmp_mpi -mpicolor 0 -in in.client -log log.client : -np 4 othercode args  # LAMMPS is client
+mpirun -np 2 othercode args : -np 4 lmp_mpi -mpicolor 1 -in in.server  # LAMMPS is server :pre
 
-Note the use of the "-mpi P" command-line argument with LAMMPS.  See
-the "command-line args"_Run_options.html doc page for further
-explanation.
+Note the use of the "-mpicolor color" command-line argument with
+LAMMPS.  See the "command-line args"_Run_options.html doc page for
+further explanation.
 
 For mode {mpi/two}, the 2 codes communicate via MPI, but are launched
 be 2 separate mpirun commands.  The specified {filename} argument is a
diff --git a/examples/message/README b/examples/message/README
index 34a5794e7a67fcc12b832a885b7f9f20cbcd9e3c..6cd99d5c097fffb8e5c09bba4fefa5dad5bb7c94 100644
--- a/examples/message/README
+++ b/examples/message/README
@@ -105,13 +105,13 @@ Mpi/one mode of messaging:
 
 Launch LAMMPS twice in a single mpirun command:
 
-% mpirun -np 2 lmp_mpi -mpi 0 -in in.message.client -v mode mpione -log log.client : -np 4 lmp_mpi -mpi 1 -in in.message.server -v mode mpione -log log.server
+% mpirun -np 2 lmp_mpi -mpicolor 0 -in in.message.client -v mode mpione -log log.client : -np 4 lmp_mpi -mpicolor 1 -in in.message.server -v mode mpione -log log.server
 
 Or run with in.message.tilt.client/server.
 
 The two -np values determine how many procs the client and the server
 run on.
 
-A LAMMPS executable run in this manner must use the -mpi color
-command-line option as their first option, where color is set to
-one integer value for the 1st app, and another value for the 2nd app.
+A LAMMPS executable run in this manner must use the -mpicolor color
+command-line option as its first option, where color is set to one
+integer value for the 1st app, and another value for the 2nd app.
diff --git a/examples/message/Script.sh b/examples/message/Script.sh
index 0125bdd500cc5797b38267e8f95e1e5a64f72024..fdcd6f11888448eb40e9425873257a7a9773b0b6 100644
--- a/examples/message/Script.sh
+++ b/examples/message/Script.sh
@@ -13,7 +13,7 @@ mpirun -np 1 lmp_mpi -v mode zmq -log log.message.server.zmq.g++.1 < in.message.
 mpirun -np 1 lmp_mpi -v mode mpitwo -log log.message.client.mpitwo.g++.1 < in.message.client & 
 mpirun -np 1 lmp_mpi -v mode mpitwo -log log.message.server.mpitwo.g++.1 < in.message.server
 
-mpirun -np 1 lmp_mpi -mpi 0 -in in.message.client -v mode mpione -log log.message.client.mpione.g++.1 : -np 1 lmp_mpi -mpi 1 -in in.message.server -v mode mpione -log log.message.server.mpione.g++.1 
+mpirun -np 1 lmp_mpi -m 0 -in in.message.client -v mode mpione -log log.message.client.mpione.g++.1 : -np 1 lmp_mpi -m 1 -in in.message.server -v mode mpione -log log.message.server.mpione.g++.1 
 
 # message on 2/4 procs each
 
@@ -28,7 +28,7 @@ mpirun -np 4 lmp_mpi -v mode zmq -log log.message.server.zmq.g++.4 < in.message.
 mpirun -np 2 lmp_mpi -v mode mpitwo -log log.message.client.mpitwo.g++.2 < in.message.client & 
 mpirun -np 4 lmp_mpi -v mode mpitwo -log log.message.server.mpitwo.g++.4 < in.message.server
 
-mpirun -np 2 lmp_mpi -mpi 0 -in in.message.client -v mode mpione -log log.message.client.mpione.g++.2 : -np 4 lmp_mpi -mpi 1 -in in.message.server -v mode mpione -log log.message.server.mpione.g++.4
+mpirun -np 2 lmp_mpi -m 0 -in in.message.client -v mode mpione -log log.message.client.mpione.g++.2 : -np 4 lmp_mpi -m 1 -in in.message.server -v mode mpione -log log.message.server.mpione.g++.4
 
 # message.tilt on 1 proc each
 
@@ -40,7 +40,7 @@ mpirun -np 1 lmp_mpi -v mode zmq -log log.message.tilt.server.zmq.g++.1 < in.mes
 mpirun -np 1 lmp_mpi -v mode mpitwo -log log.message.tilt.client.mpitwo.g++.1 < in.message.tilt.client & 
 mpirun -np 1 lmp_mpi -v mode mpitwo -log log.message.tilt.server.mpitwo.g++.1 < in.message.tilt.server
 
-mpirun -np 1 lmp_mpi -mpi 0 -in in.message.tilt.client -v mode mpione -log log.message.tilt.client.mpione.g++.1 : -np 1 lmp_mpi -mpi 1 -in in.message.tilt.server -v mode mpione -log log.message.tilt.server.mpione.g++.1 
+mpirun -np 1 lmp_mpi -m 0 -in in.message.tilt.client -v mode mpione -log log.message.tilt.client.mpione.g++.1 : -np 1 lmp_mpi -m 1 -in in.message.tilt.server -v mode mpione -log log.message.tilt.server.mpione.g++.1 
 
 # message.tilt on 2/4 procs each
 
@@ -52,4 +52,4 @@ mpirun -np 4 lmp_mpi -v mode zmq -log log.message.tilt.server.zmq.g++.4 < in.mes
 mpirun -np 2 lmp_mpi -v mode mpitwo -log log.message.tilt.client.mpitwo.g++.2 < in.message.tilt.client & 
 mpirun -np 4 lmp_mpi -v mode mpitwo -log log.message.tilt.server.mpitwo.g++.4 < in.message.tilt.server
 
-mpirun -np 2 lmp_mpi -mpi 0 -in in.message.tilt.client -v mode mpione -log log.message.tilt.client.mpione.g++.2 : -np 4 lmp_mpi -mpi 1 -in in.message.tilt.server -v mode mpione -log log.message.tilt.server.mpione.g++.4
+mpirun -np 2 lmp_mpi -m 0 -in in.message.tilt.client -v mode mpione -log log.message.tilt.client.mpione.g++.2 : -np 4 lmp_mpi -m 1 -in in.message.tilt.server -v mode mpione -log log.message.tilt.server.mpione.g++.4
diff --git a/src/lammps.cpp b/src/lammps.cpp
index dec4a57186e0ee443fb4460669fc676ebae58b54..fcdfecf30a83795d742504e43ae12a9e0dd7bdc3 100644
--- a/src/lammps.cpp
+++ b/src/lammps.cpp
@@ -879,6 +879,7 @@ void LAMMPS::help()
           "-in filename                : read input from file, not stdin (-i)\n"
           "-kokkos on/off ...          : turn KOKKOS mode on or off (-k)\n"
           "-log none/filename          : where to send log output (-l)\n"
+          "-mpicolor color             : which exe in a multi-exe mpirun cmd (-m)\n"
           "-nocite                     : disable writing log.cite file (-nc)\n"
           "-package style ...          : invoke package command (-pk)\n"
           "-partition size1 size2 ...  : assign partition sizes (-p)\n"