Colorize multi-valued field changes distinctly

beets/ui/__init__.py

@@ -1048,6 +1048,18 @@ def print_newline_layout(
 FLOAT_EPSILON = 0.01
 
 
+def _multi_value_diff(field: str, oldset: set[str], newset: set[str]) -> str:
+    added = newset - oldset
+    removed = oldset - newset
+
+    parts = [
+        f"{field}:",
+        *(colorize("text_diff_removed", f"  - {i}") for i in sorted(removed)),
+        *(colorize("text_diff_added", f"  + {i}") for i in sorted(added)),
+    ]
+    return "\n".join(parts)
+
+
 def _field_diff(
     field: str, old: FormattedMapping, new: FormattedMapping
 ) -> str | None:
@@ -1063,6 +1075,11 @@ def _field_diff(
     ):
         return None
 
+    if isinstance(oldval, list):
+        if (oldset := set(oldval)) != (newset := set(newval)):
+            return _multi_value_diff(field, oldset, newset)
+        return None
+
     # Get formatted values for output.
     oldstr, newstr = old.get(field, ""), new.get(field, "")
     if field not in new:
@@ -1071,8 +1088,7 @@ def _field_diff(
     if field not in old:
         return colorize("text_diff_added", f"{field}: {newstr}")
 
-    # For strings, highlight changes. For others, colorize the whole
-    # thing.
+    # For strings, highlight changes. For others, colorize the whole thing.
     if isinstance(oldval, str):
         oldstr, newstr = colordiff(oldstr, newstr)
     else:

docs/changelog.rst

@@ -28,6 +28,7 @@ Other changes
   values: |semicolon_space|. For example ``beet modify albumtypes="album; ep"``.
   Previously, ``\␀`` was used as a separator. This applies to fields such as
   ``artists``, ``albumtypes`` etc.
+- Improve highlighting of multi-valued fields changes.
 
 2.6.2 (February 22, 2026)
 -------------------------

test/ui/test_field_diff.py

@@ -1,3 +1,5 @@
+from textwrap import dedent
+
 import pytest
 
 from beets.library import Item
@@ -38,6 +40,19 @@ class TestFieldDiff:
             p({"mb_trackid": None}, {"mb_trackid": "1234"}, "mb_trackid", "mb_trackid:  -> [text_diff_added]1234[/]", id="none_to_value"),
             p({}, {"new_flex": "foo"}, "new_flex", "[text_diff_added]new_flex: foo[/]", id="flex_field_added"),
             p({"old_flex": "foo"}, {}, "old_flex", "[text_diff_removed]old_flex: foo[/]", id="flex_field_removed"),
+            p({"albumtypes": ["album", "ep"]}, {"albumtypes": ["ep", "album"]}, "albumtypes", None, id="multi_value_unchanged"),
+            p(
+                {"albumtypes": ["ep"]},
+                {"albumtypes": ["album", "compilation"]},
+                "albumtypes",
+                dedent("""
+                    albumtypes:
+                    [text_diff_removed]  - ep[/]
+                    [text_diff_added]  + album[/]
+                    [text_diff_added]  + compilation[/]
+                """).strip(),
+                id="multi_value_changed"
+            ),
         ],
     )  # fmt: skip
     @pytest.mark.parametrize("color", [True], ids=["color_enabled"])