4x2@16" is the default in the US for all studwalls. Check your tape measure, every 16" the numbers are different colours for a reason. So you can mark out your spacing on the top and sole planks easily.
Probably overkill for a shed. But it's what I'd do.
You're quite right about the different colours on the tape measure.
Having used the same tape measure for 30 years, I hadn't noticed - I had to go and check.
How does anyone maintain a tape measure for 30 years? Isn't the riveted lip attachment all wobbly by now adding a couple of 16/ths to every measurement?
4x2@16" is the default in the US for all studwalls. Check your tape measure, every 16" the numbers are different colours for a reason. So you can mark out your spacing on the top and sole planks easily.
Probably overkill for a shed. But it's what I'd do.