diff --git a/src/base.js b/src/base.js
index f9356da..e43792f 100644
--- a/src/base.js
+++ b/src/base.js
@@ -201,6 +201,30 @@
             }
         },
 
+        /**
+         * Setup colorMap from options
+         */
+        initColorMap: function() {
+            var colorMap = this.options.get('colorMap');
+	    if ($.isFunction(colorMap)) {
+                this.colorMapFunction = colorMap;
+            } else if ($.isArray(colorMap)) {
+                this.colorMapFunction = function(sparkline, options, index, value) {
+                    if (index < colorMap.length) {
+                        return colorMap[index];
+                    }
+                    // else undefined
+                };
+            } else if (colorMap) {
+                if (colorMap.get === undefined) {
+                    colorMap = new RangeMap(colorMap); 
+                }
+                this.colorMapFunction = function(sparkline, options, index, value) {
+                    return colorMap.get(value);
+                }
+            }
+        },
+
         /**
          * Actually render the chart to the canvas
          */
diff --git a/src/chart-bar.js b/src/chart-bar.js
index de0e376..34177e3 100644
--- a/src/chart-bar.js
+++ b/src/chart-bar.js
@@ -130,17 +130,7 @@
             }
             this.yoffset = yoffset;
 
-            if ($.isArray(options.get('colorMap'))) {
-                this.colorMapByIndex = options.get('colorMap');
-                this.colorMapByValue = null;
-            } else {
-                this.colorMapByIndex = null;
-                this.colorMapByValue = options.get('colorMap');
-                if (this.colorMapByValue && this.colorMapByValue.get === undefined) {
-                    this.colorMapByValue = new RangeMap(this.colorMapByValue);
-                }
-            }
-
+            this.initColorMap();
             this.range = range;
         },
 
@@ -167,22 +157,22 @@
         },
 
         calcColor: function (stacknum, value, valuenum) {
-            var colorMapByIndex = this.colorMapByIndex,
-                colorMapByValue = this.colorMapByValue,
+            var colorMapFunction = this.colorMapFunction,
                 options = this.options,
                 color, newColor;
-            if (this.stacked) {
-                color = options.get('stackedBarColor');
-            } else {
-                color = (value < 0) ? options.get('negBarColor') : options.get('barColor');
-            }
-            if (value === 0 && options.get('zeroColor') !== undefined) {
-                color = options.get('zeroColor');
-            }
-            if (colorMapByValue && (newColor = colorMapByValue.get(value))) {
+
+            if (colorMapFunction && (newColor = colorMapFunction(this, options, valuenum, value))) {
                 color = newColor;
-            } else if (colorMapByIndex && colorMapByIndex.length > valuenum) {
-                color = colorMapByIndex[valuenum];
+            }
+            else {
+                if (this.stacked) {
+                    color = options.get('stackedBarColor');
+                } else {
+                    color = (value < 0) ? options.get('negBarColor') : options.get('barColor');
+                }
+                if (value === 0 && options.get('zeroColor') !== undefined) {
+                    color = options.get('zeroColor');
+                }
             }
             return $.isArray(color) ? color[stacknum % color.length] : color;
         },
diff --git a/src/chart-tristate.js b/src/chart-tristate.js
index 6b2771b..a997614 100644
--- a/src/chart-tristate.js
+++ b/src/chart-tristate.js
@@ -16,16 +16,7 @@
             this.values = $.map(values, Number);
             this.width = width = (values.length * barWidth) + ((values.length - 1) * barSpacing);
 
-            if ($.isArray(options.get('colorMap'))) {
-                this.colorMapByIndex = options.get('colorMap');
-                this.colorMapByValue = null;
-            } else {
-                this.colorMapByIndex = null;
-                this.colorMapByValue = options.get('colorMap');
-                if (this.colorMapByValue && this.colorMapByValue.get === undefined) {
-                    this.colorMapByValue = new RangeMap(this.colorMapByValue);
-                }
-            }
+            this.initColorMap();
             this.initTarget();
         },
 
@@ -44,19 +35,15 @@
         },
 
         calcColor: function (value, valuenum) {
-            var values = this.values,
-                options = this.options,
-                colorMapByIndex = this.colorMapByIndex,
-                colorMapByValue = this.colorMapByValue,
+            var options = this.options,
+                colorMapFunction = this.colorMapFunction,
                 color, newColor;
 
-            if (colorMapByValue && (newColor = colorMapByValue.get(value))) {
+            if (colorMapFunction && (newColor = colorMapFunction(this, options, valuenum, value))) {
                 color = newColor;
-            } else if (colorMapByIndex && colorMapByIndex.length > valuenum) {
-                color = colorMapByIndex[valuenum];
-            } else if (values[valuenum] < 0) {
+            } else if (value < 0) {
                 color = options.get('negBarColor');
-            } else if (values[valuenum] > 0) {
+            } else if (value > 0) {
                 color = options.get('posBarColor');
             } else {
                 color = options.get('zeroBarColor');