I see. The way of painting of these bands depends on how these strips are large and how many colours there were.
One of the easiest ways is using of masks of course. You have to cut quite narrow strips of masking tape and wrap them around a spinner.Certainly the main colour should be applies on the spinner before that.
Also, you can achieve a good effect using a brush and something that can make the spinner rotating quite slow.
The next way you can use, is to make a few cardboard circles ( templates) with holes made centrally and put onto the spinner.The diameter of these holes is determined by edges of bands.