This plum tree should produce pink blossoms, so I've been looking forward to them since last month as I did last year, but so far I've seen only white blossoms.
Scientifically, white flowering plum trees produce white blossoms while pink flowering plum trees, like this one, produce pink and white blossoms depending on whether they have sufficient anthocyanins to make the flowers red (or pink). Apparently, the tree doesn't have enough anthocyanins.
Because of the mechanism, pink flowering plum trees sometimes produce half and half colored blossoms. (Read this post!).