Wanna hear something funny? You want to SAND and PRIMER those Rock Rails before you install them anyway (I have the same ones).
Standard Grey PRIMER is close to what you want. Try it... Primer rubs off on the trail as good as ANY old paint... Remember, they're rock SLIDERS...you want paint that SLIDES too!
You ARE going to primer them anyway, right??? Get an extra can or two for your garage...you will want the paint for your post trail cleaning and inspection (Daily drivers like me do this goofy shit...:confused1 ).
Want to hear a cool trick to mark the holes before you drill? Put the rails in place using Jacks, C-Clamps and Jackstands then go back and spray Flourescent orange paint in all the holes the bolts go through and wait an hour. Drop the rail from it's place and VOILA!! All your drill holes are marked for ya!!!!
Zipzipzip!!!

GREAT choice on your rockrails!! They make good steps for puttin shit up top too! Non-skid strips might be needed...slippery when wet.
Mine paid for themselves the first time out.