
There was some dev post in the official lore forums that said that crossbreeds between the clans are possible (and there was some NPC with a Keeper look but Seeker name or the other way around). Because of that, we can assume that crossbreeds are possible and that they take on the looks of whichever clan...which means that it will be impossible to tell a crossbreed apart from their 'pure' counterparts unless she's named differently (like a Sun Seeker looking Miqo'te with a Keeper name, or vice versa). Unless your character goes out of her way to tell people that she is a crossbreed, nobody will notice. And if they do, well, I don't think anyone is going to do more than raise an eyebrow before continuing interactions normally.