Inverting color on IPhone twelve

This is the forum for Photos on Mac, so I have no idea about you phone. But on a Mac (to my surprise!) you can use Preview to do this. I copied something from Notes that was written with blue on white:

and turned it into yellow (the opposite of blue) on black.

In Preview I used Tools>Adjust Color. In the Levels Window, the sliders at the bottom control the amount of light and dark.

You can grab the right one; move it to the left; grab the left one; move it all the way to the right; and then finish the leftward move of the former right one-- reversing light and dark! Wow--who knew you could do this?

Hey Laughing Water,

From what we understand, you're wanting to invert colors. Here's an article that should help with changing a windows background color in the Preview on a Mac: Change a window’s background color in Preview on Mac.

Take care.