A very merry yellow.
The whole flower clump, pink base to waving stamens, is barely 1/2 inch long.
Same flowers, different lighting.
The previous photos were taken under my halogen desk lamp; for this one, I used a small LED flashlight, which gives a very blue light. It whitens the yellow, but shows off the pink tips of the six petals.
I don't know what tree this is; I'll have to wait for the leaves to attempt an ID.