When I broke both cobblestone and granite with a diamond pick, I started to notice that the items being dropped (Cobblestone and Granite respectively) were tinted blue for a brief moment before appearing normal again.
It took me a few tries to get the timing right for a screenshot but I managed to capture the bug with granite:
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Environment
OS: Windows 10 Home 1909 64bit
Java: 1.8.0_51 64bit
CPU: Intel Core i7-6700HQ
GPU: Nvidia GeForce GTX 960M
GPU Driver: 4.6.0 Nvidia 441.20
I can confirm this in 1.15.2 (I have not tried 20w15a). When you mine, the lighting of the drops is a bit glitched when they first appear.