color selector: no field face at all — frame over the host plate

de6b1f1 swapped the blue for the textbox background, but under the relief
themes real text wells draw NO fill (the carve alone defines them), so even
a neutral background still read as 'the color selector has a background'.
The field is now a 1px frame over the plate — drawn as four strips, since
the old construction (border quad under fill quad) turns into a solid slab
the moment the fill goes transparent. Border greys and caret unchanged.

 src/widget/input/color_selector.rs | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/widget/input/color_selector.rs b/src/widget/input/color_selector.rs
index cf3ddc6..df83e47 100644
--- a/src/widget/input/color_selector.rs
+++ b/src/widget/input/color_selector.rs
@@ -171,11 +171,13 @@ impl Paint for ColorSelector {
         let pick_x = rect.x + rect.width * 0.65;
         let pick_w = rect.width * 0.35;
 
-        // The text field stays colorless: one configurable textbox background
-        // regardless of editing (the TextBox convention — the caret is the
-        // editing affordance), and neutral greys for the border. The old blue
-        // editing bg/border were this widget's own invention.
-        let bg_color = crate::colors::textbox_background_color();
+        // The text field has NO face of its own — a frame over the host plate,
+        // like a relief TextBox well (transparent fill, the outline defines
+        // it) and the closed-dropdown convention. The first colorless pass
+        // used the textbox background here, but under the DE's relief themes
+        // real text wells draw no fill, so even a neutral one read as "the
+        // color selector has a background". Neutral greys for the frame; the
+        // caret is the editing affordance.
         let border_color = if self.editing {
             [0.45, 0.45, 0.52, 1.0]
         } else if self.hovered {
@@ -184,8 +186,13 @@ impl Paint for ColorSelector {
             [0.18, 0.18, 0.24, 1.0]
         };
 
-        quads.push((rect.x, rect.y, rect.width, visual_h, border_color));
-        quads.push((rect.x + 1.0, rect.y + 1.0, rect.width - 2.0, visual_h - 2.0, bg_color));
+        // A real frame, not a border-quad-under-fill-quad: with no fill, the
+        // old full-rect border quad would read as a solid slab.
+        let bw = 1.0;
+        quads.push((rect.x, rect.y, rect.width, bw, border_color));
+        quads.push((rect.x, rect.y + visual_h - bw, rect.width, bw, border_color));
+        quads.push((rect.x, rect.y, bw, visual_h, border_color));
+        quads.push((rect.x + rect.width - bw, rect.y, bw, visual_h, border_color));
 
         if self.editing {
             let font_size = 12.0;