... Right, you're proving my point. You're using the brown for the outline instead of the purple, which when combined with the brown elsewhere in the mug you get a weird fade effect that doesn't quite work. Also another part of the problem is you darkened the outline and shadow color but didn't do anything about the hair or skin colors which is causing contrast between those as well as armor/body area. You really want to try and keep similar saturation pallet when you're doing mugs otherwise you get things that don't look quite right.
To make sure I'm following you here: We agree that in the original mug, the same dark
purple tone is used both for the deepest shadows and most of the outlines, right? Furthermore, in my edited mug, the same dark
brown tone is used for the corresponding shadows and outlines, right?
If I understand you correctly, your recommendations are to use a dark purple instead of brown for the outlines and shadows, and make that purple lighter than the brown is in the current mug. Is this correct?
For context, here's Arnold's current mug next to the original, Bowtie's (the latest one, I think), and Gig's:
Time for some investigation. Bowtie's mug uses a very dark purple (56,32,64) for both shadows and outlines. Gig's uses the same dark purple for the outlines. The proto-Arnold mug uses a less dark purple (88,64,96). The light skin tone (248,248,208) is the same in all four sprites. If I replaced my dark brown (64,34,32) with the dark purple, and perhaps darkened the lighter outlines on Arnold's hair a bit, then everything would be nice and consistent, right?