Q:

Why does rainbow() gives me an # followed by 8 digits rather 6?

I tried the function rainbow(3) in R to give me some rainbow colours. However the string that got output was 
"#FF0000FF" "#00FF00FF" "#0000FFFF"

I was only expect 6 digits after #. How come it's giving 8 digits? Does it have to do with me using a 64 bit machine? How do I convert the above to 6 digits only?

A:

I think you will get a better R color education by looking at:
?rgb
?col2rgb
demo('colors')

