Everyones eyes are different though, I have brown eyes and my pupils are pretty big even when I am not stoned or tripping. Found some more information:
Q: I would like to know if a person's pupils become dilated when he/she is high on marijuana. Do the eyes always become red?

A: Back in 1971, the Los Angeles Police Department wanted data to show that marijuana dilated pupils the way hallucinogens like LSD did. A study at UCLA showed that it often contracted pupils, but not enough to serve as a reliable indicator of intoxication. Contracted pupils often accompany a decrease in pressure in the eye, so this study actually inspired some of the first work to apply medical cannabis to glaucoma. Some people's eyes get red, but others don't.
Among other findings, the Zinberg and Weil study disproved the commonly held notion that marijuana causes a dilation of the pupils This "fact" had been so prominently believed by the general public that it was often used by the police as a cause for searching a residence for illicit drugs. Some drugs do cause a dilation of the pupils, but marijuana Is not one of them. This basic error is typical of the state of marijuana "research" until the 1960s, before which, apparently, nobody had thought to study the drug scientifically. The misconception about dilated pupils arose in the first place, Zinberg and Weil speculated, because smokers were using marijuana in darkened rooms; that, and not the drug, accounted for the change.