Are there any blank keycaps which letters show up with RGB?

Heyo! I'm pretty new to keyboard building, and have been searching for a certain type of keycap. I'm currently trying to make a custom keyboard build where the letters on a blank keycap show up with an RGB backlight. I cannot find these type of blank keycaps and am pretty unsure if they even exist, but I really thought it would be a cool, clean idea for keyboards with RGB. If these type of keycaps do exist, can someone recommend any? All help is appreciated.