Obvious color bumps in vertically striped scarf

Yeah, they’re annoying and unsightly. Anything I can do to get rid of them?

Since you’re knitting in garter, you can’t avoid the bumps showing on both sides.
However, if you work the first and last stitch of each color in stockinette (knit on the right side, purl on the wrong side), you’ll avoid the bumps on at least one side.

But wouldn’t my stockinette curl the scarf?

Oh okay! So only during the color change would I purl (on the wrong side), leaving the rest of the stitches knit?

Yes–only those two stitches would be purled on the ws row.