Hi hotbot
If you have kids the one you really want to stay away from is Tartrazine which manufacturers try to hide by using its E-number, 102. This is known to cause hyperactivity in children, amongst tens of other worrying effects on both children an adults. It is a red food colouring and when mixed with other colours can be used as a yellow (custard) or green colour (tinned peas).
If you are squeamish you may want to steer clear of cochineal which is made from the crushed shell of the female cochineal beetle. I've seen a bottle of red food colouring in Tesco that was labelled "artificial cochineal", can you guess what the colouring was? Yes good old E102, tartrazine. Devious buggers these manufacturers aren't they?
You ask if they are detrimental to your health and if so why do they allow it? Well, artifiial colours are cheap to make and cheap means more profit. Things are changing though. If you've seen the latest smarties advert, they make a big hoohaa out of the fact that they no longer contain artificial colouring.
Contrary to what CP says there are literally hundreds of non-natural food colourings still in use which are known to have detrimental effects on your health.
If it's not something you do already you should start reading the contents label on your foodstuffs. It'll scare the pants off you - or at least it should.
YF