Colorizing Individual Keys on Virtual Keyboard

[gpropf]

This is my first post here. I am considering getting an Android tablet for my mom who has macular degeneration. She currently uses these sticky orange markers on certain keys on her desktop to navigate around the keyboard (she still has partial vision). I want to know if there is a virtual keyboard where I could simulate that effect (not the tactile feel but merely the appearance). I want something fairly large - 10" would be nice. Right now she prints a lot of things and carries them with her but I think I could save on printer ink and paper if I got her a tablet she can use. Mainly she prints recipes so she can take them in the kitchen. I want something in maybe the $180-$300 range but no more.