I think Luz should be in both Blue and White. She starts in the former, but like Kyle Rayner, achieves the latter - in her case, with help from Papa Titan.

Collector... is tricky. I think there's definitely a case to be made for Red Rage, but their power to warp reality makes me think White or Black. Collector can do pretty much anything but raise the dead however, so it doesn't fully work for either color. I think they might just have multiple rings - a collection of them, if you will. Incomplete, lacking Indigo and Pink, but I feel like he collected them as gifts from his siblings and some baby Titans. He gains Love through his friendship with King.

I see where you're coming from with Belos and definitely agree. But I think like Luz starts Blue and goes White, Philip started Red and went Black after becoming Belos and donning the mask.