Both Brassard yarns.
Yes, they are different shades of red, but they also behaved quite differently in the weaving and wet finishing.
Is this uncommon?
Actually? No. It is frequently a cause of lamentations and woe when someone purchases yarn from a supplier, combines them in a textile only to discover they wind up with very different rates of shrinkage. Or other cause for consternation.
Which is one reason why I don't very often use big bold solid stripes of colour.
The brighter red *may* have been spun with fewer twists per inch. I didn't look at it that closely, to be honest. Neither did I use them in the same cloth. Because I've had other colours behave differently, too, like the forest green.
Erring on the side of caution, I tend to use these yarns either thoroughly 'mixed' (to equalize whatever differences they may have) or strictly all by themselves.
After wet finishing, one of the reds looks 'fuzzy', the red and white blend more, making a sort of pink (no there was no fugitive dye in the water - I checked - it *is* red, after all) and generally feels 'smoother' than the other. Which leads me to believe that the difference is in the tpi. But again, I didn't actually check, so I could be wrong.
While all else was equal - they were woven on the same warp - the rates of shrinkage were different as well. They were also wet finished at the same time, so IF there was fugitive dye *both* towels ought to be tinted pink. And they are not.
The yarns beat in differently, so even though they have the same number of picks per towel, the fuzzy one is longer than the other. It is also narrower, so higher shrinkage rate of the weft of this particular red than the other.
None of these things makes either towel 'wrong'. It's just different. Because...it depends...
So, same supplier, different results. Why?
Well, my stash is (ahem) elderly, and the yarns may have been purchased many years apart. Therefore there *may* have been a change of some sort - different spinning mill, different set up for spinning, etc. One of the things I learned when I ordered yarn directly from the spinning mill was that *I* needed to tell *them* the technical details of what I wanted them to do - i.e. twists per inch for the singles and the ply. Even so, mistakes were made from time to time, like the one time I got a shipment of singles 6 instead of the 2/8 I ordered. The mill took the shipment back, no question, when they looked up my order, saw that I had NOT ordered energized single 6s...
Most weavers don't have a lot of knowledge about how yarn is made. I suggest they learn. If nothing else, The Intentional Weaver will give an overview of fibre characteristics and very basic information on what to look for in a yarn.