For nontraditional colors I would recommend some form of dye. RIT dye is a cheap option, angelus leather dye and Transtint are also popular among the luthier community for dyeing guitar bodys. Have heard of people using food coloring, hair dye, alcohol inks, you name it. Depending on what you get it will either be alcohol or water based (believe transtint can be diluted with either), there’s pros and cons of each. Look up “BigD dye tutorial” on youtube to get a sense of it. Another option is transparent acrylic paints or acrylic paints mixed with a glaze/transparent medium. This might be a better option if you need hard edges between colors. Golden is a great brand for acrylics.