Which are hotter - green or red chillies?

I find the large cayenne peppers are not hot anyway, the heat is in the smaller peppers, and yes I have had some hot green ones also.

Chillis will in general develop heat the longer they are on the plant up to the point they are fully ripe.   However certain varieties develop a sweetness (eg;  Jalepenos) which isn't always wanted.

Also if you want hot green chillis you need to find the point of ripeness and work back from that.  

So let the first ones go ripe, then pick the ones that set pods just that little bit later, they should be max heat for the green stage.

Early green pods are often quite bitter and totally lacking in flavour & heat.

However cayennes are not particularly hot if you want hotter you should pick a nice bird variety, african bird (malawi/zimbabwe bird not bad), a thai hot variety or goat weed not bad.  Or you could step up the heat/flavour and go a chinense type (eg:habenaro/scotch bonnet), some varieties amongst the hottest you could wish for and if your really mad on heat then theres always the Naga morich, bhut jolokia, 7 pot or trinidad scorpion or even the humble chocolate hab.  Just keep the milk/yoghurt handy and a few rolls of loo paper in the fridge.

It definately depends on the variety more than the colour.

I'd be careful with the hotter chilli's as there are some real * out there that you think will be ok and BHAM !!!! (speaks from painful experience with an Apache chilli !!!   ooooh it still hurts)

And as an ex chef I can confirm that you shouldn't touch anywhere delicate after cutting chilli's.... if you get my drift.....  trust me , just don't.

I grew some plants from a packet titled "Hot Chilli Shake"
one had light green peppers on it about 3 inches long, so I thought I would use one in some onion relish I was making and as I wasputting it in I tried a bit about 2mm square, my lips were burning for 20 minutes after it.
Problem is I dont know the variety, as I say started light green and the rest have now gone bright red, the chilli's stick up rather than hang down, anybody got any Idea what they are ?