diff --git a/src/c3nav/mapdata/render/engines/base.py b/src/c3nav/mapdata/render/engines/base.py
index 494fff10..1425a84f 100644
--- a/src/c3nav/mapdata/render/engines/base.py
+++ b/src/c3nav/mapdata/render/engines/base.py
@@ -1,10 +1,11 @@
 import math
 from abc import ABC, abstractmethod
-from functools import lru_cache
 from typing import Optional
 
 from shapely.geometry import JOIN_STYLE, box
 
+from c3nav.mapdata.utils.color import color_to_rgb
+
 
 class FillAttribs:
     __slots__ = ('color', 'opacity')
@@ -60,14 +61,8 @@ class RenderEngine(ABC):
         pass
 
     @staticmethod
-    @lru_cache()
     def color_to_rgb(color, alpha=None):
-        if color.startswith('#'):
-            return (*(int(color[i:i + 2], 16) / 255 for i in range(1, 6, 2)), 1 if alpha is None else alpha)
-        if color.startswith('rgba('):
-            color = tuple(float(i.strip()) for i in color.strip()[5:-1].split(','))
-            return (*(i/255 for i in color[:3]), color[3] if alpha is None else alpha)
-        raise ValueError('invalid color string!')
+        return color_to_rgb(color, alpha=None)
 
     def add_group(self, group):
         pass
diff --git a/src/c3nav/mapdata/render/renderer.py b/src/c3nav/mapdata/render/renderer.py
index a67c7c18..06c6912b 100644
--- a/src/c3nav/mapdata/render/renderer.py
+++ b/src/c3nav/mapdata/render/renderer.py
@@ -7,6 +7,7 @@ from c3nav.mapdata.render.engines.base import FillAttribs, StrokeAttribs
 from c3nav.mapdata.render.geometry import hybrid_union
 from c3nav.mapdata.render.renderdata import LevelRenderData
 from c3nav.mapdata.render.utils import get_full_levels, get_min_altitude
+from c3nav.mapdata.utils.color import color_to_rgb, rgb_to_color
 
 
 class MapRenderer:
@@ -109,12 +110,22 @@ class MapRenderer:
                     for color, color_obstacles in height_obstacles.items():
                         print(height, color)
                         for obstacle in color_obstacles:
-                            engine.add_geometry(
-                                obstacle,
-                                fill=FillAttribs(color or '#B7B7B7'),
-                                stroke=None if color else StrokeAttribs('#888888', 0.05, min_px=0.2),
-                                category='obstacles'
-                            )
+                            if color:
+                                fill_rgb = color_to_rgb(color)
+                                stroke_color = rgb_to_color((*((0.75*i) for i in fill_rgb[:3]), fill_rgb[3]))
+                                engine.add_geometry(
+                                    obstacle,
+                                    fill=FillAttribs(color),
+                                    stroke=StrokeAttribs(stroke_color, 0.05, min_px=0.2),
+                                    category='obstacles'
+                                )
+                            else:
+                                engine.add_geometry(
+                                    obstacle,
+                                    fill=FillAttribs('#B7B7B7'),
+                                    stroke=StrokeAttribs('#888888', 0.05, min_px=0.2),
+                                    category='obstacles'
+                                )
 
             # add walls, stroke_px makes sure that all walls are at least 1px thick on all zoom levels,
             walls = None
diff --git a/src/c3nav/mapdata/utils/color.py b/src/c3nav/mapdata/utils/color.py
new file mode 100644
index 00000000..6b7ae5b0
--- /dev/null
+++ b/src/c3nav/mapdata/utils/color.py
@@ -0,0 +1,17 @@
+from functools import lru_cache
+
+
+@lru_cache()
+def color_to_rgb(color, alpha=None):
+    if color.startswith('#'):
+        return (*(int(color[i:i + 2], 16) / 255 for i in range(1, 6, 2)), 1 if alpha is None else alpha)
+    if color.startswith('rgba('):
+        color = tuple(float(i.strip()) for i in color.strip()[5:-1].split(','))
+        return (*(i/255 for i in color[:3]), color[3] if alpha is None else alpha)
+    raise ValueError('invalid color string!')
+
+
+@lru_cache()
+def rgb_to_color(rgb):
+    # noinspection PyStringFormat
+    return 'rgba(%d, %d, %d, %.1f)' % (*(i*255 for i in rgb[:3]), rgb[3])