Full colour is when your whole hair is coloured with ONE colour, (bleach or dye) to the roots.
Foils is when you have sections of your hair coloured and you can have more than one colour in this way. I have a couple of different blondes in mine. You can have the whole head, half head or top section done depending on the look you're going for. I have whole / top / half / top / whole / top - in that order about every 2 or 3 months to keep my colour. It's cheaper than having the whole head done every time and much, much, much better for your hair.
Love messing about with my hair.
I can only guess that full color means you're coloring every hair on your head one single color, and half-head foils means highlights.
I like dye in streaks my hair.
Full colour is when you couloir your hair in one colour and half head foils I when you put a different colour in your hair, similar to streaks