From the wriggly website:
SUGAR, GLUCOSE SYRUP, HYDROGENATED VEGETABLE FAT, ACIDS (E330, E296, E334, E331),MODIFIED STARCH, DEXTRIN, MALTODEXTRIN, FLAVOURINGS, COLOURS (E100,E120,E132,E133,E160E,E171), GLAZING AGENT(CARNAUBA WAX),VEGETABLE OIL, ANTIOXIDANT E300.
E120 isn't vegetarian or vegan I'm afraid (The website I linked is actually pretty good for looking up ingredients, not sure how reliable it is but is has almost anything I've tried to look up on there.)
I think it's really cheeky E120 has at least four names, E120, cochineal, carmine or carminic acid. I didn't realise the last two were E120 for ages and ages.
Skittles have changed their ingredients! No more E120, completely suitable for vegetarians, and from what I can tell, suitable for vegans as well.
(I've only checked the 'original' flavour ones though. Fingers crossed that the sour ones are also ok, I used to love those!)
More: Are Skittles vegan, vegetarian or halal? | Metro News (3. November 2017)The Limited Edition ‘Once in a blue moon’ Skittles are not suitable for vegetarians, vegans or those practising halal and the Wild Berry flavour is also non-halal.