Colour: Light colours, off-whites will make the room appear (psychologically) more open and spacious. Darker colours will make it feel more cosy, smaller. A lot depends on your preference for colour, but depending on the type of meditation you will use, colour may make a significant difference. If you meditate with eyes closed, it matters little which colour you use, but if you meditate with eyes slightly open, or wide open colour may set the right mood. If you use more exotic modes of meditation; ie looking at a light source, like a candle flame, darker colours would be preferable. Some folk like austere, plain surroundings to meditate in, others like to surround themselves with images of a spiritual or natural nature.
These are just a few ideas. It's up to you to determine which, if any, suite your specific needs. After all, meditation is all about YOU.
I've never touted a book before, but I recently picked up a book that looked childish in presentation, but had some excellent advice for people seeking inner serenity, it's called "Making a change for Good" by Cheri Huber, Shambala Press.
best Wishes
Geoff