Mini skeins are fabulous! I use them as a way to try new dyers or colorways, easy to purchase a few to support a new local yarn shop, and a fantastic way to try new colors outside of your regular palette.
DIY Rainbow Shawl is the second installment of the Leading Men Fiber Arts quarter designs from All Knit Up Designs. You can check out the 'in-house designer' post here.
The original sample used a variety of dye styles; tonal, speck and variegated but they were all 20 grams. You could also use all 10 grams or 50 grams if you'd prefer. The slip stitch edges give a clean and crisp finish with a nice i-cord bind off. Any minis with a base you're comfortable wearing around your neck are perfect.
If you'd prefer to use the two color garter technique with less colors and bigger skeins you can check out Dillon or Splash. If you'd like a crescent shape vs a triangle Me Before Brioche is for you. I can't wait to see the Rainbow you come up with!