Some blocks and items are discolored when viewing from certain angles

Also affects leather armor, tipped arrow, lily pad, (tall) grass, (large) fern, vines, and potions.

It's more white in the right hand when your location coordinates are -90.0 / 64.0 or 90.0 / -64.0.
e.g.

/tp @s ~ ~ ~ -90.0 64.0

And for the left hand it's 90.0 / 64.0 or -90.0 / -64.0.

As for banners, both of these location coordinates are affected for both hands.

All items are affected, but some of them are just getting darker or brighter basing on view angle too

That's a related but distinct issue, see MC-163105.

Seems to be fixed in 19w42a.

Yeah it fixed for all but for banners it still not fixed so I have created a new ticket : MC-163877

Confirmed for 19w42a. Only partially fixed.