With GIMP I can replaced a specific color with another color instead, instead of having so recolor every pixel individually.
you don't have to recolor every pixel individually....
You can either use the bucket to change color in large areas, or use the eraser to change color.
To use the eraser:
1. Use the "pick color"-tool (right under the "eraser"-tool.
2. left click on the colored area you want to change.
3. right click on the color you want to change to.
4. Select the eraser.
5. Increase or decrease the size of the eraser, by holding down left-"CTRL" and the plus (+) sign on the numpad. realize the buttons when you come to the size you want.
6. hold down RIGHT mouse button (not the left button) and move the eraser over that color you want to replace and only that color will be replaced.
The advantage of this you can recolor a small area without extra work and you have a lot of flexibility.