This looks like it could be a shader/material mismatch issue with SkeletonGraphic. Here are the most likely causes and things to check:
Check your shader assignment
The shaders compatible with SkeletonGraphic are Spine/SkeletonGraphic and Spine/SkeletonGraphic Tint Black. If your skeleton was originally set up as a SkeletonAnimation and then moved onto a canvas, the original shader may have carried over and remained unchanged. Please verify the shader selected in your material settings:
Check your texture import settings — sRGB vs Linear
A very common cause of slots appearing darker than expected is a mismatch between the texture's color space setting and how the shader expects to read it. Make sure your atlas textures have the correct sRGB (Color Texture) setting. If a texture is imported as linear when it should be sRGB (or vice versa), certain slots can appear darker or lighter than they look in the Spine editor.
Check Premultiplied Alpha (PMA)
Your atlas export and material shader need to agree on whether premultiplied alpha is being used. If your atlas was exported with PMA enabled but your material/shader is not set up for PMA (or vice versa), you can get unexpected darkening artifacts on certain attachments — especially ones with semi-transparent regions or specific blend modes.
Check slot and skeleton tint colors
Make sure neither the affected slot nor the skeleton itself has an unintended tint color applied at runtime. You can verify this with something like:
var skeleton = GetComponent<SkeletonGraphic>().Skeleton;
var slot = skeleton.FindSlot("yourSlotName");
Debug.Log($"Slot color: {slot.R}, {slot.G}, {slot.B}, {slot.A}");
Debug.Log($"Skeleton color: {skeleton.R}, {skeleton.G}, {skeleton.B}, {skeleton.A}");
If any of those values are less than 1.0, the slot or skeleton is being tinted darker. Note that if your animations key those slot color values, any manual changes will be overwritten — so be sure to check after animations have been applied.
Why only certain slots?
It being limited to a few specific slots (like the cheeks) is a strong hint that it's either a per-slot color being set (either in the animation data or at runtime), or those specific attachments/regions have a different texture page that has different import settings compared to the rest of the skeleton.
A good debugging step would be to check if those affected slots share the same texture atlas page as the ones that look correct, or if they ended up on a separate page during export.
