I saw this post on Emily A. Clark about painting faux bias twill tape lines down your bamboo shades. I happen to have bamboo shades in my sewing room and thought this was a GREAT idea.
But instead of using paint I just used black duct tape! Did this in just 10 minutes! I didn't even have to remove the blinds from the hooks. I just started the tape at the bottom and unrolled it as I went. I used the lines on the roller shade as a guide so I didn't even need a ruler. After you are done roll up the blinds to the top for a couple hours to allow the tape to adhere to the shades.
And honestly, it looks as good as twill tape. If you want to see another window shade post I did with Duck Tape check out this post where I make roller shades chic with a Greek Key shape!