Also try a counter-intuitive setting by lowering the backlight, not raising it.
currently with:
backlight: 45
brightness: -1
contrast: +3
I get a really blue sky (the sky was my reason for choosing HDR), with a vibrant, but natural, green vegetation
The perception of color is very subjective so I can’t guarantee that you’ll see the same things, but also I thought I had to raise the brightness to have more vivid colors, but the risk is to burn them and lose contrast.