just select an icon by clicking on it and a color by clicking on it. click on the button that says:"color (number 1 or 2)" to switch the part of the icon you are changing the color of.
i am new to scratch. so i try to recreate gd in it and i started with the icon editor. so i share the progress with you guys! please report bugs if you find them in the comments or just give me ideas in the comments