@@ -73,28 +73,34 @@
         bg=None,
         palette={
             None: ("#FFFDE7", "#C9BC5B", "#6B6420"),
-            Manual: ("#E7F3EC", "#2F7D5B", "#1B5138"),
-            Lookup: ("#F2F4F7", "#A9B1BD", "#495261"),
-            Computed: ("#FBEAEC", "#B23A48", "#7C2430"),
-            Imported: ("#E2ECFA", "#2A5FA5", "#123A6D"),
-            Part: ("#FFFFFF", "#9AA6B8", "#46536B"),
+            Manual: ("#E8F0E9", "#3E7A52", "#28513A"),
+            Lookup: ("#F0F0F1", "#808285", "#5A5C5F"),
+            Computed: ("#FFEDE5", "#FF5113", "#B23200"),
+            Imported: ("#E0F4FC", "#00A0DF", "#00537A"),
+            # Part text is #55585C rather than Lookup's #5A5C5F only so every
+            # light color maps to exactly one role (the adaptive block requires
+            # a collision-free mapping); visually identical.
+            Part: ("#FFFFFF", "#B9BBBE", "#55585C"),
             "collapsed": ("#EDEEF0", "#808890", "#404040"),
         },
-        edge="#3A424F",
+        # Edges and titles are brand navy. The schema-cluster frame is #171D3A —
+        # one step off navy for the same collision-free reason (edge and frame
+        # are both strokes and need distinct dark counterparts).
+        edge="#171C39",
         edge_renamed="#C77D3A",
         edge_alpha="9E",
-        schema_cluster=("gray", "gray"),
+        schema_cluster=("#171D3A", "#171C39"),
         entity_fill="#F3F5F8",
     ),
     "dark": dict(
         bg="#161A21",
         palette={
             None: ("#3A3620", "#C9BC5B", "#EBE3A0"),
-            Manual: ("#16281F", "#4FA97F", "#BCE6CF"),
-            Lookup: ("#242832", "#8A93A1", "#C9CFD9"),
-            Computed: ("#331A1F", "#D0687A", "#F3C2CB"),
-            Imported: ("#152538", "#5E92D6", "#C3DAF6"),
-            Part: ("#1E232C", "#7B879B", "#C4CCDB"),
+            Manual: ("#16281F", "#6BBF94", "#BCE6CF"),
+            Lookup: ("#242832", "#9DA0A4", "#C9CFD9"),
+            Computed: ("#331B12", "#FF7A47", "#FFC7AE"),
+            Imported: ("#0F2433", "#33B8E8", "#BEE7F9"),
+            Part: ("#1E232C", "#8F959D", "#C8CED8"),
             "collapsed": ("#242730", "#8890A0", "#C7CDD6"),
         },
         edge="#AEB6C2",
@@ -1811,7 +1817,7 @@ def make_mermaid(self) -> str:
         --------
         >>> print(dj.Diagram(schema).make_mermaid())
         flowchart TB
-            classDef manual fill:#E7F3EC,stroke:#2F7D5B,color:#1B5138
+            classDef manual fill:#E8F0E9,stroke:#3E7A52,color:#28513A
             ...
             subgraph my_pipeline["my_pipeline"]
                 Mouse[Mouse]:::manual
@@ -1820,7 +1826,7 @@ def make_mermaid(self) -> str:
             end
             Mouse --> Session
             Session --> Neuron
-            linkStyle 0 stroke:#3A424F,stroke-width:1px
+            linkStyle 0 stroke:#171C39,stroke-width:1px
         """
         graph = self._make_graph()
         direction = self._connection._config.display.diagram_direction
 
@@ -79,10 +79,10 @@ def test_light_theme_style(schema_by_backend):
     ctx = _build(schema_by_backend)
     svg = _svg(schema_by_backend, ctx, "light")
     # tier fills
-    for fill in ("#e7f3ec", "#f2f4f7", "#e2ecfa", "#fbeaec", "#ffffff"):
+    for fill in ("#e8f0e9", "#f0f0f1", "#e0f4fc", "#ffede5", "#ffffff"):
         assert fill in svg, f"light tier fill {fill} missing"
     # a couple tier strokes
-    for stroke in ("#2f7d5b", "#b23a48"):
+    for stroke in ("#3e7a52", "#ff5113"):
         assert stroke in svg, f"light tier stroke {stroke} missing"
     # thick (1:1) and thin (multi) edge weights both present
     assert 'stroke-width="2"' in svg, "thick (1:1) edge missing"
@@ -97,7 +97,7 @@ def test_dark_theme_style(schema_by_backend):
     ctx = _build(schema_by_backend)
     svg = _svg(schema_by_backend, ctx, "dark")
     assert "#161a21" in svg, "dark background missing"
-    for fill in ("#16281f", "#152538", "#331a1f"):
+    for fill in ("#16281f", "#0f2433", "#331b12"):
         assert fill in svg, f"dark tier fill {fill} missing"
 
 
@@ -108,7 +108,7 @@ def test_auto_theme_is_adaptive(schema_by_backend):
     svg = _svg(schema_by_backend, ctx, "auto")
     assert "@media (prefers-color-scheme: dark)" in svg, "auto theme must inject the adaptive media block"
     # base render is light; the media block maps a light color to its dark counterpart
-    assert "#e7f3ec" in svg and "#16281f" in svg, "auto theme must carry both light base and dark override colors"
+    assert "#e8f0e9" in svg and "#16281f" in svg, "auto theme must carry both light base and dark override colors"
 
 
 def test_mermaid_matches_modernized_notation(schema_by_backend):
@@ -138,8 +138,8 @@ class Analysis(dj.Computed):
     mmd = dj.Diagram(schema, context=ctx).make_mermaid()
 
     # shared light-theme palette (classDefs), not the old bright colors
-    assert "classDef manual fill:#E7F3EC,stroke:#2F7D5B" in mmd
-    assert "classDef computed fill:#FBEAEC,stroke:#B23A48" in mmd
+    assert "classDef manual fill:#E8F0E9,stroke:#3E7A52" in mmd
+    assert "classDef computed fill:#FFEDE5,stroke:#FF5113" in mmd
     assert "#90EE90" not in mmd, "old bright palette must be gone"
 
     # cardinality edge weights via linkStyle: thick 1:1 and thin one-to-many both present
@@ -150,7 +150,42 @@ class Analysis(dj.Computed):
 
     # renamed FK takes the theme's amber; ordinary edges the slate
     assert "stroke:#C77D3A" in mmd, "renamed-FK amber missing"
-    assert "stroke:#3A424F" in mmd, "ordinary edge slate missing"
+    assert "stroke:#171C39" in mmd, "ordinary edge navy missing"
 
     # master-part group nests in an entity subgraph
     assert "subgraph entity_" in mmd, "master-part entity nesting missing"
+
+
+def _contrast(fg, bg):
+    def lum(h):
+        c = [int(h.lstrip("#")[i : i + 2], 16) / 255 for i in (0, 2, 4)]
+        c = [x / 12.92 if x <= 0.03928 else ((x + 0.055) / 1.055) ** 2.4 for x in c]
+        return 0.2126 * c[0] + 0.7152 * c[1] + 0.0722 * c[2]
+
+    hi, lo = sorted([lum(fg), lum(bg)], reverse=True)
+    return (hi + 0.05) / (lo + 0.05)
+
+
+def test_theme_text_contrast_meets_aa():
+    """Every tier's text-on-fill pair holds WCAG AA (>= 4.5:1) in both themes (#1543)."""
+    for name, theme in dj.diagram._DIAGRAM_THEMES.items():
+        for tier, (fill, _stroke, text) in theme["palette"].items():
+            ratio = _contrast(text, fill)
+            assert ratio >= 4.5, f"{name}/{tier}: {text} on {fill} = {ratio:.2f} < 4.5"
+
+
+def test_adaptive_mapping_is_collision_free():
+    """Every light color maps to exactly one dark counterpart per attribute (#1532 invariant)."""
+    light, dark = dj.diagram._DIAGRAM_THEMES["light"], dj.diagram._DIAGRAM_THEMES["dark"]
+    for idx, kind in ((0, "fill"), (1, "stroke"), (2, "fill")):
+        mapping = {}
+        for tier in light["palette"]:
+            lv, dv = light["palette"][tier][idx].lower(), dark["palette"][tier][idx]
+            assert mapping.setdefault((kind, lv), dv) == dv, f"collision on {kind} {lv}"
+    strokes = {}
+    for lv, dv in [
+        (light["edge"].lower(), dark["edge"]),
+        (light["edge_renamed"].lower(), dark["edge_renamed"]),
+        (light["schema_cluster"][0].lower(), dark["schema_cluster"][0]),
+    ]:
+        assert strokes.setdefault(lv, dv) == dv, f"stroke collision on {lv}"