UI: Theme: Make nodes use the exact theme color

Make node headers (or body when collapsed) use the exact theme color
set for that node type, instead of a hardcoded blend between it and the
node backdrop.

This can result in unreadable combinations, but allows more
flexibility and it is consistent with the rest of Blender.

Both dark and light theme defaults have been updated.

See PR for details and screenshots.

Pull Request: https://projects.blender.org/blender/blender/pulls/140481

release/datafiles/userdef/userdef_default_theme.c

@@ -804,23 +804,23 @@ const bTheme U_theme_default = {
     .grid_levels = 3,
     .dash_alpha = 0.5f,
     .syntaxl = RGBA(0x303030ff),
-    .syntaxs = RGBA(0x973c3cff),
-    .syntaxb = RGBA(0xcccc00ff),
-    .syntaxn = RGBA(0xff3371ff),
-    .syntaxv = RGBA(0x12adffff),
-    .syntaxc = RGBA(0x3b660aff),
-    .syntaxd = RGBA(0x4c9797ff),
+    .syntaxs = RGBA(0x5a3838ff),
+    .syntaxb = RGBA(0x6e6e23ff),
+    .syntaxn = RGBA(0x82354cff),
+    .syntaxv = RGBA(0x246283ff),
+    .syntaxc = RGBA(0x374725ff),
+    .syntaxd = RGBA(0x3e5a5bff),
     .syntaxr = RGBA(0x8d8d8dff),
-    .nodeclass_output = RGBA(0x4d0017ff),
-    .nodeclass_filter = RGBA(0x551a80ff),
-    .nodeclass_vector = RGBA(0x4d4dffff),
-    .nodeclass_texture = RGBA(0xe66800ff),
-    .nodeclass_shader = RGBA(0x24b524ff),
-    .nodeclass_script = RGBA(0x084d4dff),
+    .nodeclass_output = RGBA(0x3e232aff),
+    .nodeclass_filter = RGBA(0x412b51ff),
+    .nodeclass_vector = RGBA(0x3c3c83ff),
+    .nodeclass_texture = RGBA(0x79461dff),
+    .nodeclass_shader = RGBA(0x2b652bff),
+    .nodeclass_script = RGBA(0x203c3cff),
     .nodeclass_pattern = RGBA(0x6c696fff),
     .nodeclass_layout = RGBA(0x6c696fff),
-    .nodeclass_geometry = RGBA(0x00d6a3ff),
-    .nodeclass_attribute = RGBA(0x001566ff),
+    .nodeclass_geometry = RGBA(0x1d725eff),
+    .nodeclass_attribute = RGBA(0x1d2546ff),
     .node_zone_simulation = RGBA(0x66416233),
     .node_zone_repeat = RGBA(0x76512f33),
     .node_zone_foreach_geometry_element = RGBA(0x33527f33),