Following the recent on-list debate surrounding the colouration and function of speculated dinosaur plumage, I've taken to looking at my tatty old book on some european birds of prey. I noticed that all the birds' feathers (with the possible exception of Pernis aviporus, the honey buzzard) were of the following colours:
4. Anywhere within the brown spectrum between peach and terra-cotta
These are not exactly vivid colours. It was interesting to note that any with bright colour had it in their eyes or on their skin, not their plumage(specifically their feet and cere). The following colours were noted on the skin:
1. Yellow - most common. Token example Accipiter nissus (sparrowhawk)
2. Pink - ranges from subtle human skin colour with Gyps fulvus (griffon vulture) to more "mother-of-the-bride" shades, ie, Falco vespertinus (red-footed falcon)
3. Grey - not the brightest of things to be sure. Found in Elanoides forficatus (swallow-tailed kite) among others.
4. Orange? - Neophron percnoterus (Egyptian vulture) picture is a little unclear, could be a solarised yellow.
5. Blue! - the cere of Aegypius monachus (European Black vulture). I also recall (from memory, so beware!) seeing a raptor with blue feet.
In addition to these observations, I remember red skin and I think purple? in a couple of other raptors (anyone have any ideas what these were? is there a predatory bird expert in the house?). So, the overall trend with at least modern feathered archosaurs is for camouflage colours using pattern for display on the plumage and actual vivid colours when present on the skin.
Bearing in mind the hand of speculation is looming large, and heeding the cautions about using modern animals to compare to ancient ones - does this bode well at all for more colourful featherless theropods? (picture if you will a Daspletosaurus with blue legs)