Fixed a logic error in series color generation.

This addresses #906, the case where a fixed color index on a series
results in the color generator producing one color less than is actually
needed.

jquery.flot.js

@@ -439,7 +439,7 @@ Licensed under the MIT license.
             // If any of the user colors are numeric indexes, then we
             // need to generate at least as many as the highest index.
 
-            if (maxIndex > neededColors) {
+            if (maxIndex >= neededColors) {
                 neededColors = maxIndex + 1;
             }