fix: Consolidates Color/Center html (#1762)

### Summary
- Fixes bad color in virtual check gump
- Consolidates the Color/Center html strings for all gumps

Projects/UOContent/Items/Skill Items/Magical/Potions/BasePotion.cs

@@ -2,7 +2,6 @@ using System;
 using ModernUO.Serialization;
 using Server.Engines.ConPVP;
 using Server.Engines.Craft;
-using Server.Utilities;
 
 namespace Server.Items;
 

Projects/UOContent/Items/Skill Items/Ninjitsu/NinjaWeapons.cs

@@ -6,7 +6,6 @@ using Server.Spells.Chivalry;
 using Server.Spells.Necromancy;
 using Server.Spells.Ninjitsu;
 using Server.Targeting;
-using Server.Utilities;
 
 /*
  * There really was no prettier way to do this,  other than the one