I'm making a cake like a massive Caburys Twirl. Iv never 'painted' on acake and was unsure wither or not to use yellow fondant or paint on food colouring.
I read that powder foodcolpiring an vodka/gin is the best way to go about painting on fondant. But I don't know if I could use yellow on dark purple?

Any help would be appreciate

Personally, I would cut out the lettering using yellow fondant instead of painting on the letters. Especially since you are painting on a dark colour like purple, I would be afraid of the colours bleeding. Also, if you make a mistake painting it's much harder to correct where as with fondant lettering you should be able to peel it off with little damage.
That is the correct technique though, using vodka to mix with the colouring. You can also use vanilla extract.

Lemon extract is very good to paint with, since it has a higher alcohol percentage than vodka.

Lemon extract is very good to paint with, since it has a higher alcohol percentage than vodka.

As Cakes 22 stated, I'd use yellow fondant. I'd also add a bit of tylose for strength so the letters retain the shape and a tappit cutter. Clean and easy. HTH

id also cut out the letters - i just wont show up on the puple if you paint.
xx

Thanks guys. Does light food colouring show up on dark fondant? There is some small font that I want to put on the cake and using fondant for that might be difficult...I'd need to use White, yellow and red on ameythst purple fondant. Do you know if this will work?

ImMissWorld, light food coloring does not show up on dark fondant, you will need to cut out the letters with fondant or use royal icing and pipe the lettering on.