a quick trick I learned for honing in on certain parts of an image accurately ...
load up the picture in your paint program ( my choice is paintshop pro )
create a copy and make it a layer .....
erase the lips on the top layer so the painted layer shows through
then color the lower layer any way you want -
so for example you can make one render from face filter with the bozo the clown lips ....do a 2nd render with the original lips - then layer them and slowly erase the correct lips on to the original lip image. - merge both layers to 1 layer when done.
especially cool for changing eye colors - or making the whole image black and white then coloring only eyes and lips.
I hope this helps :)
☯🐉
"To define Tao is to defile it" - Lao Tzu