These things are more common in spring and early summer. I have seen Hawks, eagles and falcons all show interest in mostly slower planes. Some come quite close and stick around for sometime checking things out.
I really doubt that color plays into this much, last weekend we had a adult Bald Eagle stay over a friends big Telemaster for several mins.. He/she was clearly very interested in the big yellow/white plane slowly flying below it. There are many birds of prey in the area and we commonly see them around our field. (they are very welcome to the digging rodents that try and use our field.)