Can I color SMBC or IMBC in bright primary colors? how about purple? will I get true colors or just pastle?

I think this depends on how much colouring you put in and also what brand you use. Americolor colouring gives quite vibrant results.

thanks for the reply, so you're saying if I use a good amount of americolor I'll get true red, blue, purple etc?

Yes, you should do. It can just take quite a bit of colouring to get the colour you're after. I think there are a few different brands that other people recommend but I just can't remember the names of them at the moment.

I'm a huge fan of natural dried fruit colourings for a lot of things but you wouldn't be able to achieve a full on bright red or yellow with those, they are better for pastel shades, but I really like the flavour they give.