While color may dictate what color Pokemon appears, there are other things to consider. Number of Legendaries, for example. R/S/E has had the largest number of legendaries to date (far past being completely rediculous because of the lack of good ingame Pokemon). Had R/S/E been like R/B/Y with only one primary legendary (Mewtwo in this case), it's almost certain that Treeko/Sceptile, Torchic/Blaziken, and Mudkip/Swampert would have been the cover Pokemon of those games.
Something I'd like to mention. We have had some trends develop, and they've become almost expected. The Legendary trio, for example. The birds, the dogs, the Regis; we've come to expect every game to have these triplets of powerful, yet limited Pokemon. Along with that, each game has had a Legendary Legend that is unobtainable through normal means, and each of these Pokemon has rounded base stats at 100. Because of that, I'm going to reveal the possibility that Rukario (or Lukario if you have it that way) will be one of those Legendary Legends. It may not be part psychic, as per the pattern, but the new generation games have already dealt a blow to most preconceived patterns with the release of the four-phase Deoxys.
Another pattern that seems to have revealed itself (and also one that worries me) is the growing number of legends. RBY had Mewtwo, the singular Super Legendary. GSC had Ho-Oh and Lugia, a pair of Super Legendaries. But RSE has had THREE Super Legendaries in Kyogre, Groudon, and Rayquaza! Based on this pattern, Diamond and Pearld will either have... two or four Super Legendaries. I hope it's two, because four is simply rediculous.