There used to be this handy command in Chimera to color oxygen atoms and nitrogen atoms specific colors:

color @O red,a 

color @N blue,a

but I can't find the corresponding command in ChimeraX. Is there a way to color all nitrogen atoms blue and all oxygen atoms red?
When I try what I think the equivalent command should be (I'm displaying cartoon backbone with stick side chains):

color @O red target a

color @N blue target a

it says 'Colored 1120 atoms' but none of the sidechains are colored differently.

Thanks for the help

Liz