In that case a decent i3 and the top of the range mosaic setup is definitely your best bet :-)

Couple the mosaic with a formbot raptor: https://www.formbot3d.com/formbot-ra...ing-p0022.html
And for under $2000 you've got a multi coplour/multi media setup that will print 400x400x500mm :-)

Check with mosaic people that it'll work with a raptor - can't see why it wouldn't. ut always worth a check anyway.

As far as your other query goes. rgb models - not a clue :-)

Also no idea how you'd go about designing full colour parts eithger - I currently only use openscad and while i can make dual colour/material models. It's just by making the model in 2 interconnecting parts.

For a full colour print you'd need a cad setup that knew about colours. Ask mosaic what they recommend.