Fix setPatternColor on tropical fish bucket meta

Prior to this commit, the tropical fish bucket meta would set the body
color to the previous metas pattern colour when updating the pattern
colour.

This commit hence simply fixes this by using the proper body colour
value when updating the pattern color.

paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaTropicalFishBucket.java

@@ -128,7 +128,7 @@ class CraftMetaTropicalFishBucket extends CraftMetaItem implements TropicalFishB
         if (this.variant == null) {
             this.variant = 0;
         }
-        this.variant = CraftTropicalFish.getData(color, this.getPatternColor(), this.getPattern());
+        this.variant = CraftTropicalFish.getData(color, this.getBodyColor(), this.getPattern()); // Paper - properly set tropical fish pattern color without mutating body color
     }
 
     @Override

paper-server/src/test/java/io/papermc/paper/inventory/CraftMetaTropicalFishBucketTest.java

@@ -0,0 +1,41 @@
+package io.papermc.paper.inventory;
+
+import org.bukkit.DyeColor;
+import org.bukkit.Material;
+import org.bukkit.entity.TropicalFish;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.meta.TropicalFishBucketMeta;
+import org.bukkit.support.environment.AllFeatures;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+@AllFeatures
+public class CraftMetaTropicalFishBucketTest {
+
+    @Test
+    public void testAllCombinations() {
+        final var rawMeta = new ItemStack(Material.TROPICAL_FISH_BUCKET).getItemMeta();
+        Assertions.assertTrue(rawMeta instanceof TropicalFishBucketMeta, "Meta was not a tropical fish bucket");
+
+        final var meta = (TropicalFishBucketMeta) rawMeta;
+
+        for (final var bodyColor : DyeColor.values()) {
+            for (final var pattern : TropicalFish.Pattern.values()) {
+                for (final var patternColor : DyeColor.values()) {
+                    meta.setBodyColor(bodyColor);
+                    Assertions.assertEquals(bodyColor, meta.getBodyColor(), "Body color did not match post body color!");
+
+                    meta.setPattern(pattern);
+                    Assertions.assertEquals(pattern, meta.getPattern(), "Pattern did not match post pattern!");
+                    Assertions.assertEquals(bodyColor, meta.getBodyColor(), "Body color did not match post pattern!");
+
+                    meta.setPatternColor(patternColor);
+                    Assertions.assertEquals(pattern, meta.getPattern(), "Pattern did not match post pattern color!");
+                    Assertions.assertEquals(bodyColor, meta.getBodyColor(), "Body color did not match post pattern color!");
+                    Assertions.assertEquals(patternColor, meta.getPatternColor(), "Pattern color did not match post pattern color!");
+                }
+            }
+        }
+    }
+
+}