I thought a green one was nickel and a blue one was magnesium, but I’m no expert and have only seen a few examples with distinct coloration. The blue one was odd, from my vantage point it appeared to come straight down. UNC lost a big basketball game that night, so it led to some amusing comments about symbolizing Carolina’s basketball season.
Iv’e never seen a red one so I will keep an eye out for it. I don’t claim to be an expert either.
There is an opinion that supports what you said about nickel.
Why is a meteor Green?
A: The bright green color of some meteorites is caused by the internal combustion of metals as they pass through the upper atmosphere. Many asteroids are rich in nickel and have trace amounts of copper. Both metals burn green when sufficiently heated.
What causes a green shooting star? | Reference.com
www.reference.com/science/causes-green-shooting-star-fca8bec0eb3cb4b
However, Carolina lost to Kentucky a few nights earlier. :-)