there are so many kinds of green and red hot peppers, and it is a bit difficult to say which one is hotter. there are green peppers that are hotter then some red peppers and the reverse applys too.
All pepers start green and as they ripen they become red, yellow orange and even purple.
some rule of thumb say that the smaller the peppers the hotter they are and the brighter the peppers the hotter they are.
anyhow - to see how hot is a particular pepper you have and to compare it to other kinds see a couple of gallerys:
Pictorial guide to peppers
A Gallery of red and green peppers
If you want to learn the chemistry behind hot peppers see The Heat Scale this site has a scale of all chillis and ranks them by how hot they are, if you scroll down you will see the checmical explanation behind all this.