Initially starting swatching on 3.5mm but that was clearly so far from gauge I ripped out and restarted on 3.75mm.

Swatch 1: 3.75mm/3.25mm
Forgot to start with smaller sized needle, but did go down for final rows and ribbing along steek edges, so the swatch is distorted (wider at bottom than at top), which surely doesn’t help things!
As my colourwork is much tighter than my plain knitting, need to go down 2 rather 1 needle size for cast on, ribbing, and bind off.
Gauge (both pre and post blocking) = 27 sts / 31 rows.

Although this swatch isn’t the correct gauge, I’m really pleased to have practised steeking as I’ve never done this before. Will definitely benefit from having another practice on the second swatch.

For this swatch I held squall to the right of whatever other colour featured in the row. For the next swatch I’m going to reverse this to see what visual affects the dominance has.

Swatch 2: 4mm/3.5mm
CO & 3 k 3 rounds on 3.5mm, switching to 4mm for chart, back to 3.5mm for final plain rows, cast off and side ribbing.
Gauge (after light steam, pre-steeking) 25 sts / 31 rows
Forgot to switch down to 3.5 needle for bind off! Argh. Looking at the bottom of the swatch 3.5 definitely looks like the right match for 4mm gauge size needle. Will use 3.5mm for practising the puk rib edging.