diff --git a/range.c b/range.c
index 103c136..d6d17eb 100644
--- a/range.c
+++ b/range.c
@@ -1624,7 +1624,6 @@ enum {
     COL_USER = COL_GRID,
     COL_ERROR,
     COL_LOWLIGHT,
-    COL_HIGHLIGHT = COL_ERROR, /* mkhighlight needs it, I don't */
     COL_CURSOR = COL_LOWLIGHT,
     NCOLOURS
 };
@@ -1649,7 +1648,7 @@ static float *game_colours(frontend *fe, int *ncolours)
 {
     float *ret = snewn(3 * NCOLOURS, float);
 
-    game_mkhighlight(fe, ret, COL_BACKGROUND, COL_HIGHLIGHT, COL_LOWLIGHT);
+    game_mkhighlight(fe, ret, COL_BACKGROUND, -1, COL_LOWLIGHT);
     COLOUR(ret, COL_GRID,  0.0F, 0.0F, 0.0F);
     COLOUR(ret, COL_ERROR, 1.0F, 0.0F, 0.0F);
 
diff --git a/singles.c b/singles.c
index 6c35162..42ecdbe 100644
--- a/singles.c
+++ b/singles.c
@@ -82,7 +82,7 @@ bool verbose = false;
 #define FLASH_TIME 0.7F
 
 enum {
-    COL_BACKGROUND, COL_HIGHLIGHT, COL_LOWLIGHT,
+    COL_BACKGROUND, COL_UNUSED1, COL_LOWLIGHT,
     COL_BLACK, COL_WHITE, COL_BLACKNUM, COL_GRID,
     COL_CURSOR, COL_ERROR,
     NCOLOURS
@@ -1620,12 +1620,13 @@ static float *game_colours(frontend *fe, int *ncolours)
     float *ret = snewn(3 * NCOLOURS, float);
     int i;
 
-    game_mkhighlight(fe, ret, COL_BACKGROUND, COL_HIGHLIGHT, COL_LOWLIGHT);
+    game_mkhighlight(fe, ret, COL_BACKGROUND, -1, COL_LOWLIGHT);
     for (i = 0; i < 3; i++) {
         ret[COL_BLACK * 3 + i] = 0.0F;
         ret[COL_BLACKNUM * 3 + i] = 0.4F;
         ret[COL_WHITE * 3 + i] = 1.0F;
         ret[COL_GRID * 3 + i] = ret[COL_LOWLIGHT * 3 + i];
+        ret[COL_UNUSED1 * 3 + i] = 0.0F; /* To placate an assertion. */
     }
     ret[COL_CURSOR * 3 + 0] = 0.2F;
     ret[COL_CURSOR * 3 + 1] = 0.8F;
diff --git a/tracks.c b/tracks.c
index 9b5ef4c..afb9ff9 100644
--- a/tracks.c
+++ b/tracks.c
@@ -2463,8 +2463,7 @@ static void game_set_size(drawing *dr, game_drawstate *ds,
 }
 
 enum {
-    COL_BACKGROUND, COL_LOWLIGHT, COL_HIGHLIGHT,
-    COL_TRACK_BACKGROUND = COL_LOWLIGHT,
+    COL_BACKGROUND, COL_TRACK_BACKGROUND,
     COL_GRID, COL_CLUE, COL_CURSOR,
     COL_TRACK, COL_TRACK_CLUE, COL_SLEEPER,
     COL_DRAGON, COL_DRAGOFF,
@@ -2477,7 +2476,7 @@ static float *game_colours(frontend *fe, int *ncolours)
     float *ret = snewn(3 * NCOLOURS, float);
     int i;
 
-    game_mkhighlight(fe, ret, COL_BACKGROUND, COL_HIGHLIGHT, COL_LOWLIGHT);
+    game_mkhighlight(fe, ret, COL_BACKGROUND, -1, COL_TRACK_BACKGROUND);
 
     for (i = 0; i < 3; i++) {
         ret[COL_TRACK_CLUE       * 3 + i] = 0.0F;