diff --git a/README.rst b/README.rst
index 846481f..ec881ea 100644
--- a/README.rst
+++ b/README.rst
@@ -70,6 +70,17 @@ colors <file>:
     * For compatibility, in the current directory as a last resort.
       This causes a warning message to be printed.
 
+    If the colors file contains duplicate entries for the same node,
+    one with alpha = 255, or absent, and one with alpha < 255, the former
+    is used without 'drawalpha', and the latter is used with 'drawalpha':
+
+::
+
+    # Entry that is used without 'drawalpha':
+    default:water-source	39 66 106
+    # Entry that is used with 'drawalpha':
+    default:water-source	78 132 212 64 224
+
 bgcolor:
     Background color of image, `--bgcolor #ffffff`
 
diff --git a/TileGenerator.cpp b/TileGenerator.cpp
index 5bab022..c1ad2b6 100644
--- a/TileGenerator.cpp
+++ b/TileGenerator.cpp
@@ -344,6 +344,28 @@ void TileGenerator::parseColorsStream(std::istream &in, const std::string &filen
 		t = 0;
 		iline >> t;
 		color = ColorEntry(r,g,b,a,t);
+		if ((m_drawAlpha && a == 0xff) || (!m_drawAlpha && a != 0xff)) {
+			// If drawing alpha, and the colors file contains both
+			// an opaque entry and a non-opaque entry for a name, prefer
+			// the non-opaque entry
+			// If not drawing alpha, and the colors file contains both
+			// an opaque entry and a non-opaque entry for a name, prefer
+			// the opaque entry
+			// Otherwise, any later entry overrides any previous entry
+			ColorMap::iterator it = m_colors.find(name);
+			if (it != m_colors.end()) {
+				if (m_drawAlpha && (a == 0xff && it->second.a != 0xff)) {
+					// drawing alpha: don't use opaque color to override
+					// non-opaque color
+					continue;
+				}
+				if (!m_drawAlpha && (a != 0xff && it->second.a == 0xff)) {
+					// not drawing alpha: don't use non-opaque color to
+					// override opaque color
+					continue;
+				}
+			}
+		}
 		m_colors[name] = color;
 	}
 	if (!in.eof()) {
diff --git a/colors.txt b/colors.txt
index baf9db9..19b12b0 100644
--- a/colors.txt
+++ b/colors.txt
@@ -1467,7 +1467,8 @@ mesecons_walllever:wall_lever_on 136 136 136
 mesecons_walllever:wall_lever_off 136 136 136
 bones:bones 74 74 74
 default:glass 192 192 227 64 16
-default:water_flowing 39 66 106 128 224
+default:water_flowing 39 66 106
+default:water_flowing 78 132 212 64 224
 default:junglesapling 37 34 14
 default:sandstonebrick 160 144 108
 default:furnace_active 97 93 91
@@ -1505,7 +1506,8 @@ default:desert_stone 122 74 57
 default:tree 66 52 35
 default:jungletree 120 106 78
 default:cactus 132 143 108
-default:water_source 39 66 106 128 224
+default:water_source 39 66 106
+default:water_source 78 132 212 64 224
 default:mese 200 202 0
 default:stone_with_coal 91 88 87
 default:nyancat 38 16 66