I was able to see it, Kitt.
And yeah, I see what you mean. I have a better scan of that piece on my computer, where the color looks a little brighter, but not by much. What's used on Joyleaf in that collection of pastel portraits is noticeably more yellow than what she used to color Cutter's hair in the same collection. So even when a 1-to-1 comparison can be made, Wendy seemed not to intend Joyleaf's hair to be quite the same color as Cutter's.
Also, other examples of Joyleaf art from that same year, colored by Wendy, show much more yellow hair -- such as the back cover of OQ #4. I'm not sure in precisely what year Wendy painted colored the comics for the first OQ graphic novel collection, I think it was a year or two later, but that back-cover was colored contemporaneously with the pastel portraits collection. So it seems to show that Wendy didn't necessarily intend Joyleaf to have Cutter-colored hair originally and just changed her mind later.