Let me show you the most easy way to change lips color in Photoshop fast and realistic!
Select the Brush tool and press Q to mask the lips. use soft brush and carefully select the lips.
Press Q one more time and press Ctrl + Shift + I to invert the mask
Now you can see the area that you just masked. use brush tool to do any adjustments you want to the masked area.
Click on hue/saturation and drop the saturation all the way down.
this way the natural color of the image lisps doesn't mix with the color we gonna add.
Click on the thumbnail of the mask and add solid color. use any color you want.
Change the blending to the color and there you have it!
EASY AND FAST!
Hope you find it useful, peace!
Disclaimer : I used a free stock photo on PEXELES.COM to make this post all the credits of the portrait goes to the PHTOGRAPHER.