Buy one of the dye products that you add to the washing machine,it is by far the easiest way to dye things easily.However,I have never attempted to dye rayon & have no idea if it will be a success.It is a man made fibre,not natural & NOT cotton.
Most dyes for cotton will work. Google dyeing rayon for specific instructions.
I bought some 100% bamboo rayon sheets (totally white) off Amazon and I want to dye them lavender but I don't want to ruin them :3 thanks