The Color Replacement tool allows you to paint across an area and change its color. What’s really nice about this tool is that you don’t have to be overly precise with your painting, because you’re only going to affect the painted area. Photoshop will replace only the colors that you mouse over with the crosshair that shows up in the center of the brush cursor.
This tool applies your foreground color to the active layer, so remember that you can change the foreground color by holding down the Option/Alt key and clicking an area in the image that contains the desired color.
When you paint, Photoshop uses your foreground ...