Recipe for Color Inlay:
Make the pots. Let them firm up a bit.
Etch lines in them as desired.
Lay color into the lines.
Clean up surface as required.
Bisque fire, clear glaze, glaze fire.
Voila! Color inlaid pottery.
Time it took to write this: a minute.
Time it took to learn to make the pots and do these li'l tricks nicely: 33 years.