namco/namcos21_3d.cpp: bit 7 of code really doesn't seem depth cue related

* fix aircomb 3d colors

Author: angelosa

src/mame/namco/namcos21.cpp

@@ -474,6 +474,7 @@ void namcos21_state::winrun_bitmap_draw(bitmap_ind16 &bitmap, const rectangle &c
 			// TODO: additive blending?
 			// - winrun car select uses register [0xc] for a xscroll value
 			// - winrun windshield during gameplay (reversed 0x6000 and 0x4000 bases?)
+			// NOTE: very similar to namcos21_c67_state::sprite_mix_callback
 			case 0x00:
 				pDest[sx] = (pDest[sx]&0x1fff)+0x4000;
 				break;

src/mame/namco/namcos21_3d.cpp

@@ -271,14 +271,16 @@ void namcos21_3d_device::draw_quad(int sx[4], int sy[4], int zcode[4], int color
 	else
 	{ /* map color code to hardware pen */
 		int code = color >> 8;
-		if (code & 0x80)
-		{
-			color = color & 0xff;
-			// color = 0x3e00|color;
-			color = 0x2100 | color;
-			depthcueenable = 0;
-		}
-		else
+		// TODO: aircomb dislikes this logic
+		// (not sure what would use it anyway)
+		//if (code & 0x80)
+		//{
+		//	color = color & 0xff;
+		//	// color = 0x3e00|color;
+		//	color = 0x2100 | color;
+		//	depthcueenable = 0;
+		//}
+		//else
 		{
 			color &= 0xff;
 			color = 0x3e00 | color;

src/mame/namco/namcos21_c67.cpp

@@ -1,10 +1,19 @@
 // license:BSD-3-Clause
 // copyright-holders:Phil Stroffolino
 /*
-    NOTES:
 
-    Air Combat:
-         priority issues
+TODO (2026 update):
+- how the 3d rasterizer really selects banks 1 & 2? aircomb is the odd one, it has a red shaded
+  bank from time to time;
+- aircomb: z-fighting issue on attract mode with the plane renders (after the first title screen);
+- aircomb: sprites blends badly with background pen when warning appears and the src target is the sky color
+  (i.e. pen 0xff with current handling);
+- aircomb: level select/continue screen draws with a red pen, should be pure black according to refs;
+- aircomb: missing background on attract mode ranking screen (masking? cfr. shared/namco_c355spr.cpp);
+- cybsled: https://mametesters.org/view.php?id=6302
+- solvalou: https://mametesters.org/view.php?id=2085
+- solvalou: black screen on service mode (cfr. shared/namco_c355spr.cpp);
+- starblad: 3d freezes after exiting service mode;
 
 TODO:   namcoic.c: in StarBlade, the sprite list is stored at a different location during startup tests.
         What register controls this?