P.S. Thanks randofo for the feature!
Step 1: Gather Materials
-10-20 minutes (depending on how good of a job you want to do)
-Shirt you want to hack
-Flat shoelaces (You could use round, but it I think it would look dumb, but I encourage you to try it if you want to.
-Scissors. My scissors are made by "Fiskars," which sounds like a cat food name to me.
Step 2: Match your Colors
Just round up the flat laces you have around the house, and the shirt you want to mod, and just hold them up to each other, and see what you like. You could take the shirt to a shoe store, compare them, then buy the one you like, too.
You have a lot of room to be creative, I know that they make all kinds of patterns on flat laces, including, Checkers, Spongebob, Stripes, Zigzags, and tons of colors.