Change the graphics card virtualbox to pseudocolor mode RHEL6 and RHEL7

Hello.

I have two virtual machines RHEL6 one RHEL6 and other RHEL7. For our work we need to work in pseudocolor mode. 'The Vboxvideo virtual machines have a virtual card.

Anyone know how you can change to vboxvideo work in pseudocolor mode?

thank you very much
regards
valentin