Letting Chroma do the work, with subtle color changes that will make each mitt slightly different. I am so ok with that!
(A note on the yarn: I see on the KP website that Chroma is now washable. Mine is old, and it is hand-wash only. Also, I saw a lot of comments on the uneven spinning of the singles yarn currently, but I am not experiencing any of those issues with this old ball I am using, so it is a lovely experience.)

Also, making fingerless gloves, not mittens, see mods!

Mods:
Cast on 56, inc to 60 and larger needles for colorwork.
Cuff - 20 rounds.
Change to larger needle, inc 4 evenly around.
Work chart to round 54.
Knit 1 round plain, dec 4 evenly around.
2x2 rib 8 rounds, bind off loosely.
Put thumb sts on needle, picking up 4 sts in gap. Work thumb in pattern 8 rounds, 2x2 for 8 rounds, bind off loosely.

These are a little snug. Next time, I plan to use size 3 needles as the larger size…