with Rowdy? I have tried everything even to the point of becoming "square". She's the hottest thing this side of the apocalypse. Oh yeah...Atom Cats rule!

My character has the hots for Piper Wright, but so far the dialogue option for romance is still not the same color as the rest of the dialogue options.... so who knows? lol... as my first play through, we've been "hitched" as companions since almost starting..

Are there any quests associated with the Cats? I wanted to join up with them.

And Rowdy keeps saying "we need more suits around here". I've brought her four. Nothing happens.

http://fallout.wikia.com/wiki/Atom_Cats

Seems the answer for quests is... 1

It doesn't need to be the same color for it to be an option you can pursue. The different colors are for varying levels of "difficulty" to pass the speech attempt (more likely for success with higher charisma, as well as possible armor that adds charisma points).
If "flirt" is an option, but in another color, that means you are able to attempt to flirt. Go for it.

It's bugged then. I completed that quest and the gunners attack every time I FT there. They even killed one of the Cats.

I'd love for the Atom Cats to have their mission logs and content around them expanded. They're really endearing when you talk to them and get their histories and backstories (and read Zeke's absolutely hilarious autobiography). They're decent folk who happen to like spiffing up power armor. Hell, they gave a former raider a second chance at being a decent person (Rowdy), and freely help farms in return for food (even if they poke fun about the smell) instead of taking advantage of their power armor.

There, of course, needs to be a mission to win a race on that drag strip they have with your power armor suit. That absolutely must happen.

I really wish Bethesda had added more to the 'faction'. As it is, I make sure my slick plates... err... my Cats painted T-60 stands prominently in my garage.

I have a feeling an upcoming DLC will expand on the Atom Cats Garage.

try going up to her in your "tidy whities"

You can pursue a dialogue option even if it's not the same colour. It just means your charisma (and luck) will influence the outcome. Yellow means somewhat easy, orange harder and red very hard. Characters with high charisma usually have no trouble. A low charisma character will have trouble romancing companions without clothing, drugs, etc.