definitely check that video on dying with RIT. I just did a pair of crowbars and they look flawless. It's a great leap above paint, as the color sets directly INTO the plastic whereas paint is visibly ON the plastic.
of course, with grey frames your color options are limited. So if you're hoping to go lighter than grey, painting would be the way to go. it could work with some masking tape and proper paint. it may not hold up as well against rubbing, etc. but you don't know if you don't go.
get crafty and go for it!