Keep automatic Design body colours clear of the selection colour

docs/HLSD/design-tab.md

@@ -197,7 +197,9 @@ as the body (`DesignCanvas::rebuild_bodies`); the sketch overlay outlines them w
 — a dark band under a selection-coloured one — so the outline still reads on a body that wears
 the selection colour itself. A body picked whole, a face picked in the viewport and the faces of
 the Feature tree's selected feature all draw this way. The hover pre-highlight is the outline
-alone, uncased: it promises a click, it is not one.
+alone, uncased: it promises a click, it is not one. The automatic body colours keep clear of the
+selection colour's blues and teals, so no body looks selected before anything is picked; a colour
+the user sets on a body is theirs, and the cased outline keeps its selection readable.
 
 Selecting a feature row lights the faces that feature made, not the whole body it sits on, so a
 fillet row shows its round and the extrude under it keeps the faces the fillet trimmed.

src/slic3r/GUI/CAD/DesignCanvas.cpp

@@ -227,12 +227,14 @@ DesignCanvas::~DesignCanvas()
 }
 
 // Distinct per-body colours (Onshape-style). Body 0 keeps the familiar gold; the rest
-// cycle through a small saturated palette so coexisting solids read as separate parts.
+// cycle through a small saturated palette so coexisting solids read as separate parts. No entry
+// may sit near the selection cyan (design_selection_color): a blue or teal body would look
+// selected, and its selected faces would barely stand out.
 static ColorRGBA body_palette(int body_idx)
 {
     static const ColorRGBA kPalette[] = {
         ColorRGBA(0.86f, 0.66f, 0.20f, 1.0f),  // gold
-        ColorRGBA(0.30f, 0.62f, 0.90f, 1.0f),  // blue
+        ColorRGBA(0.84f, 0.42f, 0.66f, 1.0f),  // rose
         ColorRGBA(0.45f, 0.78f, 0.42f, 1.0f),  // green
         ColorRGBA(0.86f, 0.45f, 0.40f, 1.0f),  // coral
         ColorRGBA(0.70f, 0.52f, 0.86f, 1.0f),  // violet