Add skinning support for column line colour

osu.Game.Rulesets.Mania/Skinning/LegacyColumnBackground.cs

@@ -46,6 +46,9 @@ namespace osu.Game.Rulesets.Mania.Skinning
                                       new LegacyManiaSkinConfigurationLookup(Stage?.Columns.Count ?? 4, LegacyManiaSkinConfigurationLookups.LightPosition))?.Value
                                   ?? 0;
 
+            Color4 lineColour = GetManiaSkinConfig<Color4>(skin, LegacyManiaSkinConfigurationLookups.ColumnLineColour)?.Value
+                                ?? Color4.White;
+
             InternalChildren = new Drawable[]
             {
                 new Box
@@ -57,6 +60,7 @@ namespace osu.Game.Rulesets.Mania.Skinning
                 {
                     RelativeSizeAxes = Axes.Y,
                     Width = leftLineWidth,
+                    Colour = lineColour,
                     Alpha = hasLeftLine ? 1 : 0
                 },
                 new Box
@@ -65,6 +69,7 @@ namespace osu.Game.Rulesets.Mania.Skinning
                     Origin = Anchor.TopRight,
                     RelativeSizeAxes = Axes.Y,
                     Width = rightLineWidth,
+                    Colour = lineColour,
                     Alpha = hasRightLine ? 1 : 0
                 },
                 lightContainer = new Container

osu.Game/Skinning/LegacyManiaSkinConfigurationLookup.cs

@@ -34,5 +34,6 @@ namespace osu.Game.Skinning
         HoldNoteHeadImage,
         HoldNoteTailImage,
         HoldNoteBodyImage,
+        ColumnLineColour
     }
 }

osu.Game/Skinning/LegacySkin.cs

@@ -193,6 +193,9 @@ namespace osu.Game.Skinning
 
                 case LegacyManiaSkinConfigurationLookups.ShowJudgementLine:
                     return SkinUtils.As<TValue>(new Bindable<bool>(existing.ShowJudgementLine));
+
+                case LegacyManiaSkinConfigurationLookups.ColumnLineColour:
+                    return SkinUtils.As<TValue>(getCustomColour(existing, "ColourColumnLine"));
             }
 
             return null;