What colours of coolant are offered?

I've scene green, yellow and orange.

 

green is your normal coolant
orange is your expensive environmental friendly crap
i cant think of the yellow[&:]

 

My prestone coolant is yellow.

 

my supertech is green

 

Reason I ask, is a guy at work has brown coolant. I thought well maybe its just made like that, but then I started wondering who makes it.

What would cause it to go brown?
Its a 97 Camry v6 fwiw.

 

Probably dirty or he got some oil in there.

 

Dirty coolant... usually has something to do about rust, though... I know when I had my camaro.. my radiator rusted.. and caused the block to rust too.. so yeah.. Iw oudl say soemthing is rusting.. I flushed my camaro about 10 times and never got it to clear up

 

my r/t usually has brown coolant...maybe the new motor will help make it green again[&:]