[Coda]

Long story short, the problem is gamma correction. PNG files can save gamma information inside them, which is SUPPOSED to give instructions on how to adjust the colors to look the same on any display, but in practice different screens have different color curves and trying to correct just makes everything worse.

I think web browsers these days turn gamma correction off, so you might even get different color behavior if you look at the picture in a browser as opposed to looking at it directly in Paint Tool SAI.

For your own use on your own computer, you can calibrate your screen, your image editor, and your printer, and you'd be able to have the printouts match what you have on screen fairly closely. But if you want the images to look exactly the same on different screens, you're looking at a hopeless cause.

What you CAN do -- though I don't know how to TELL you how to do it because I'm not familiar with the tools you use -- is turn off gamma correction. Then the colors in the images will be consistent relative to other colors displayed on the screen, even if the whole image is colored a little differently than it would have been if it were shown on your laptop.