Francy,
Is the "Barley" color an ACE color?
It's a popular ACE color here, and yes, it's a light tan-ish/yellow-ish color.

Depending on what Zinsser Oil you have, they can take 1 or 2 oz's of colorant/tint per gallon. It says on the can!
However, these primers have a LOT of TI02 in them, so any formula put into them (up to the tint-limit) is a lighter shade.

What was the fill-level (in Ounces...says on the bottom-front of the can) of that medium-base Fresh-Start primer??
* If it was for example 124 oz., they can add up to 6 oz's. of tint.
* This would obviously total 130 oz's., which is considered a "full" gallon. 2 more Ounces would be at 132 oz's. (a NORMAL gallon), BUT there wouldn't be any room for shaking!!
* I WOULD actually try that medium-base Primer for the Barley, since you're not "fighting so much White" in that base.
* However, Barley is a white-base (paint) color anyway, so tinting a primer isn't necessary under that color.

Faron