When I’m marking up annotations on drawings I change the display & print colour of anything with a query to red to make things easier to track. Is there any way I can assign this to a button :- select item, left click to change to red, right click to set it back to its layer defaults?
Create A New Button (In a Toolbar > rightmouse button > new button
Paste this in Left mouse button:
-_properties _pause _O _C _O 255,0,0 _enter _M _O _enter _C 255,0,0 _enter _enter
Past this in right mouse button:
-_properties _pause _O _C L _enter _enter _M _L _enter
See if it suits you 
Many thanks. Display change works perfectly. The print part of it doesn’t seem to work. Can you walk through the list of options called, then I can learn how to sort it out myself in future?!
Command macros are just as if you were stringing a bunch of commands together on the command line. You can see what each step is doing if you type these on the command line. You might find http://docs.mcneel.com/rhino/5/help/en-us/information/rhino_scripting.htm helpful.
To set the color and print color, you might want to change them to the following:
-_Properties _Pause _Object _Color _Object 255,0,0 _PrintColor _Object 255,0,0 _enter _enter
and to set it back it would be
-_Properties _Pause _Object _Color _Layer _PrintColor _Layer _enter _enter