There are plenty of parts options out there these days....
John at Midatlantic.com
Jess at Jessbikes.com
Andre or Ellen at Reproductiondecals.com
Do some comparison shopping. I purchase all of my resto items from these vendors.
and there are no paint codes. House of Kolor and Dupont Hot Hues Candies have good matches. You will need to find some sample books and find a color you think is "close enough". There were a lot of variations (shades, content of candy, etc) with Kawasaki paint back then so keep that in mind as well. Also, if you are restoring the bike with the intention of reselling to make a "profit" just because its a Kawi Triple, know that it is VERY easy to get upside down fixing these bikes up...especially the little triples.
If you restoring because you love the bike... Then good on ya! Not many people fix up 250's......