Spoon a couple tablespoons of plain frosting into plastic bag fitted with round tip.

Pipe around the perimeter of the cookie with the white frosting. This barrier will prevent the rest of the frosting from dripping off the edge of the cookies. Let dry for several minutes.

Meanwhile, prepare the colored frosting. Decide on the colors you want for your tie dye effect. Divide frosting between bowls and mix with the gel colors (gel dyes are very concentrated, and a little goes a long way!)

Transfer colored dyes to squeeze bottles.

Microwave squeeze bottles of dyed frosting, one at a time as you use them. You don't want to completely melt the frosting, just soften it enough to be able to flood. I did 8 seconds at 80% power in my microwave. Once they were warm, when I needed to reheat, I did just 3 seconds.

Shake the bottle a little, then turn upside down and trace on the inside of the white outline of the cookie. Don't squeeze too hard as softened frosting will flow out quite easily.

Repeat with other colors (warming bottles in microwave first) until the cookie is filled in.

Using a toothpick or skewer, drag frosting from the center out to create a tie dyed effect on the cookies.