You seem quite young to have grey hairs but I don't think it would make someone unattractive. If you have an attractive face I don't think the hair is all that important. The 'silver fox' look can be sexy!
I get the occasional gray hair or two try not to be stressed out.
Not a big deal, I guess. My hair too started turning grey when I was 22, and now 20% of my hair has greyed (I'm 27 now). Its not visible from a distance, but its quite noticeable up close. Even more so, because I'm dark haired. Can't really say about attractiveness because I have voluntarily chosen to remain single since 5 years. But I don't suppose grey hair would be an instant turn off.