Subject: Why are there 8 gluons?

Sir,
I have the following two questions to ask:

1. That day, I read something about the Standard Model. I learnt that there are 
3 color charges. I don't know if this is an understanding or a 
misunderstanding, but I then learnt that (y, ybar)type combination of quarks 
(where y denotes a color charge)is not allowed in a gluon. Then how are there 8 
gluons? Kindly clear my confusion out.

2. My next question is- Why do the names of most particles end in '-on'?!

Re: Why are there 8 gluons?