So, I recently got checked out a book from the Drake University Library called "The Luttrell Psalter: A Facsimile". Before I do any in-depth study, I was asked about how the color green was highlighted. So I quickly searched the book and found these instances of the color green being used (it wasn't a popular color, used maybe once every twenty pages). It appears that a rather pale green was used as a base with a darker blue/green as the shadow and white as a highlight. Here are some examples:
