i created one, but i can’t figure out how to adjust the brightness and darkness
Once you created the colour transform effect and hooked your background to it, select the first dot that shows the default zone of the effect element, then look for the properties panel and displace the three cursors red-green-blue in the multiplicative or in the aditive sections, to the left side, more left, more dark, you can investigate the best combination for your work. If you wish transparency, move the alpha cursor to the left side. Next, apply the same values selecting the last dot. You can extend the exposure of the effect just pulling the end of the thick area of the effect. Good luck. Yoryo.