Yes, they are, and yes, you can! Just make sure that the colours of the game don't pass three colours! (Shades count as colours too!)
Can the colours change from level to level? So you have for example 10 levels and each one has different colours but in every level there are maximum 3 colours... or does it need to be the same colour in every level?
Of course, you can change the colours from level to level! As long as they don't pass 3 colours
