iPhone homescreen washout colors
The only easy way I found to fix the color it’s to restart my iPhone XS after changing the wallpaper. That works for me, it got to be a bug I have this issue in iOS 12 and now 13.2
The top photo is the wallpaper with the correct color after restarting my iPhone XS and the one below is the wallpaper after applying it without a restart.
iPhone XS, iOS 13