I doubt that his pink costume was the problem — I kind of liked pink as a kid and even designed football uniforms and race cars that were pink (which wasn't quite the taboo back then that it is today — several top Indy cars of the '50s and early '60s were pink, including the 1955 winner). But Coz's uniform was kind of generic and dull (no matter what the color). With most other Legionnaires, I had my own personal ways of sprucing up the uniforms to my liking, but I never really found the combination to improve Coz's with minor alterations.
It kind of amazed me to discover that Rokk was a favorite of Keith's, but it was Keith's perception of Rokk as the moral foundation of the Legion that brought the character into focus for me. He became what I think of as a true hero, a guy who always does the right thing, no matter how difficult, and who's genuinely embarrassed and uncomfortable having his heroism pointed out and rewarded. He does it because he wants to and has to — because doing it is its own reward.
Rokk's crush on Saturn Girl seemed like a natural. I think it was hinted at in that George Tuska-drawn version of the origin where he (in addition to Garth) is seen flipping over Imra. But Rokk's heroism would dictate that he never try to "win" Imra from Garth. If Imra chose Rokk, that would be her right, but Rokk couldn't allow himself to actively try to make that happen. (As this applies to our early Legionnaires issues, remember, too, that the Garth Imra had fallen in love with was the post-death "Proty" Garth, who was everything Imra wanted, and had seemingly sacrificed his life for her. The SW6 Garth woke up with the original Garth personality, which is not the Garth Imra fell in love with, but she would have viewed this as a regression for the man she was in love with, not a different person that she could easily and quickly break up with. So the poor behavior of the SW6 Garth for the 15 Legionnaires issues we wrote would not have been enough to let either Imra or Rokk feel comfortable about pursuing an Imra-Rokk relationship. In their minds, Garth was still the guy who willingly sacrificed himself for Imra and, once he was brought back to life, had for years been an admirable, noble member of the team.
LIGHTNING LAD DIGRESSION: For those who don't remember or never could follow the twists and turns of our convoluted stories — we suggested that the original Garth really did die back in Adventure #304, and that he'd been kind of a jerk up to that point. When he was "revived," what they actually did was project the personality of Proty I into Garth's body. The real Garth really was dead and gone. But that Proty, madly in love with Imra, never revealed this unexpected twist. For her part, Imra never had the courage to delve deeply enough into "Garth's" psyche to confirm what she suspected but didn't want to believe.
Then, when the SW6 batch was created (or taken from an alternate reality, or whatever the heck their ultimate origin turned out to be), the new Garth had the original Garth's personality, so now, in the eyes of his teammates, the good-guy Garth suddenly reverted back to his old butthead ways.
Thus, Imra and Rokk weren't tolerating an insufferable jerk over the long haul, they were trying to come to grips with a good friend and noble hero who'd "fallen off the wagon" and gone back to old, unacceptable behavior patterns.
Now, many of you might point out in some frustration that we could have hinted at a lot of this — shown people saying things like, "What's gotten into Garth, lately," etc. We should have, but a couple things made it tough, one being that space was at a real premium, given that we were trying to introduce new readers to a 20-hero team, giving each member at least one or two meaty roles in our 15 issues. The other is that we really wanted this to be a complete "fresh start" book with no prior knowledge necessary. Once we hinted at this Garth-Proty thing, there'd have been tons of complex back story. If we'd had the "Mother Book" to work with, we'd have preferred to tackle all of this in an issue of that book, where readers were, at that time, definitely more used to involved continuity-bound stories.
Had we had time to get into it, we probably would have explained that the Dominators projected the Adventure #304-351 memories into the SW6 Garth, so, even though he was biologically the original roguish Garth, this SW6 Garth thought he'd had all of those adventures when he was actually the Proty Garth. For their own reasons, the Dominators probably spliced out any knowledge of the Proty presence from those memories.
Saturn Girl, meanwhile, had always been physically in lust with the original jerk Garth, but prior to his death and transformation, she could never accept his personality. After Garth's "resurrection," it probably took Proty/Garth a long time to recover from the process and figure out what had happened and who he really was. Maybe Garth's old thought waves were still prevailing. But by the time Proty got his bearings and realized who he really was, everyone had accepted Proty/Garth as the real Garth and he had won the human female he was in love with, so Proty chose not to reveal what had really happened. For her part, Imra probably always suspected the truth, but was so in love with the results of the "resurrection" that she never allowed herself to probe deeply enough to find out the whole truth, especially since Proty/Garth found ways to "guard" his thoughts. Imra would never, for selfish reasons, invade a section of a friend's mind where she wasn't welcome, so there stood the uneasy truce. Did Imra, in her heart, know the truth? Probably, but once she committed herself to living the lie, it would become a monstrously complicated and difficult lie to pull out of. And what a story it might have been to come up with the occasion when the adult Imra and Proty would finally have to face up to the whole rather grotesque truth.
As for the SW6 kids, though, it was a little different. After the SW6 batch was unleashed, Garth probably had no knowledge in his head of the Proty switch — he believed the noble Proty-Garth was really him, so Saturn Girl no longer had even any subtle telepathic evidence of the truth.
 Probably having something to do with Dominator hopes of locating and harnessing the "Soul of Antares" (James Cullen, Kid Quantum, see Legion #33), the assembled intelligence and sentience of the Proty race.
 Again, we'd have to figure out an explanation as to why the Dominators would choose to splice that knowledge out of the memories inserted in the SW6 Garth's head.