diff --git a/src/extensions/scratch3_pen/index.js b/src/extensions/scratch3_pen/index.js
index 78705a5f5..1e2940756 100644
--- a/src/extensions/scratch3_pen/index.js
+++ b/src/extensions/scratch3_pen/index.js
@@ -191,13 +191,13 @@ class Scratch3PenBlocks {
     }
 
     /**
-     * Wrap a color input into the range (0,100).
+     * Wrap a color input into the range (0,99).
      * @param {number} value - the value to be wrapped.
      * @returns {number} the wrapped value.
      * @private
      */
     _wrapColor (value) {
-        return MathUtil.wrapClamp(value, 0, 100);
+        return MathUtil.wrapClamp(value, 0, 99);
     }
 
     /**