Important: This ticket is only about the sides of those blocks being not quite the correct color. The top of grass blocks and leaves being gray is MC-161837.
The bug
The sides of grass blocks and leaves seem to be incorrectly colored in first-person mode when held in the hand. It seems like the colors are have less saturation than they should have.
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Those are the snowy textures.
I'm talking about the sides of these blocks, not the top.