"A Lytell Dye Boke"

Drea Leed of Elizabethan Costume tests historical dye recipes.  Worth a look even if your group doesn't require naturally-dyed fabrics (XMFM does not) for insight on what historical at least looks like.  Linen seems to take dye much less readily than wool, so madder linen is a dusty pink instead of a deep or rusty red, and indigo linen tends to be baby blue rather than anything approaching the deep steel blue associated with the name "indigo."