Marking default coloring (#13039)

* Marking coloring WIP

* EnsureDefault now supports coloring!

* Now markings have coloring when they get added

* Many things

* yml files

* cleanup

* Some requested changes

* Nullable type and WIP caching

* Time to resolve that thing with deprecated hair fields

* Latest reviews + im still trying to use these hair markings

* FirstOrDefault thing and Tattoo docs

* IDK

* It's now works a bit more properly in preferences GUI

* THEY SYNCING! However preferences GUI still broken and doesn't work properly

* Markings now updating when changing in GUI. However they still don't work properly with bald humanoids

* Forgor...

* Default hair-colored markings will not color to hair if there is no hair

* Fixed default colors for customizable markings

* Fixed bug in prefs GUI that set current hair to null

* Now markings that must match skin color because of limb (e.x. Slimes) - will match skin color

* final tweaks: if hair uses skin color then markings will use skin color as hair color (slimes)

* fix

* fixed dirty. no more funni invis bug

* Mirrors and client profile loading

* default colors soon TM

* review + better coloring

* Hardcode is gone

* diona markings

* oh my god

* fixed CategoryColoring

* cool fallback, clean up and some other tweaks

* code style

* more style

* a

Content.Shared/Humanoid/HumanoidVisualLayers.cs

@@ -1,4 +1,5 @@
-using Robust.Shared.Serialization;
+using Content.Shared.Humanoid.Markings;
+using Robust.Shared.Serialization;
 
 namespace Content.Shared.Humanoid
 {