How do I make an original POV-ray texture and use it in a Three.js scene?

Obviously your export from POV-Ray is not exact. It should also be able to export png.

POV-Ray - Wikipedia :
support for textures and rendered output in many image formats, including TGA, PNG, and JPEG, among others

Maybe you can get help in a POV-Ray forum?

I haven’t worked with the software myself, I only know it because my project Addon for triangulation of implicit surfaces/ forms with holes is a takeover from Pascal visualizes with POV-Ray.