I ran into a similar issue with my Interstate 75, no backlight / brightness function.
Using HSV got me what I wanted.
Interstate 74 W, how do you control the display brightness? - Support - Pimoroni Buccaneers
I know what you mean, I have several LCD based weather displays scattered around the house. Some LED matrixes too. In a dim or dark room they can be very distracting. I’ve setup auto brightness using light sensors where I can.
Understanding the GU light sensor - Support - Pimoroni Buccaneers