Is there a way to tell aseprite when changing color on a image, like i want to change all greens at once to a certain type of green at once or change all background colors to one type of color
Just select Paint Bucket Tool (one with ‘drop’ icon), then disable [ ] Contiguous mode and specify your Tolerance value (0=only exactly same colors will be replaced … 255=all colors will be replaced) at top panel for it to paint. NOTE: With Contiguous mode disabled it will work over all suitable colors in whole picture i.e. not just like paint spreading, but like replacement of colors.
Keep in mind that non-contiguous Paint Bucket Tool will only affect one layer at a time. Remember to replace your colours in all the layers.
An alternative, if your art has <= 256 colours in total, is to make your image into an Indexed image, and adjust the colour in the palette to whatever new colour you want. You can change it back to RGB afterwards.