Another Thing about Dyeing

I really don’t understand this next bit.  Perhaps someone (G-G?) with more dyeing experience can let me know.

This is the yarn I just dyed.

This is the yarn I’d used most of the chartreuse on, around 2004.

They look pretty similar, right?  Well, here is the pic I posted last week:  the poncho you see in the 2004 photo, after it was finished.  So it’s 6 years old.

Look how yellow this is!

This last photo is definitely what I call chartreuse.  The other ones look like lime, or grass green, in places.  I might have believed that the dye in the jar had changed color over time, except that the photo of the beginning of the poncho matches the stuff I just dyed last week.  So it makes me wonder if this glove will fade/alter to a much yellower green over time…?  Anyone know?