Fixed optional alpha parameter in interpolateColor.

Author: calvindavis

typescript/phaser.d.ts

@@ -755,7 +755,7 @@ declare module Phaser {
         static HSVtoRGB(h: number, s: number, v: number, out?: ColorComponents): ColorComponents;
         static HSVColorWheel(s?: number, v?: number): ColorComponents[];
         static hueToColor(p: number, q: number, t: number): number;
-        static interpolateColor(color1: number, color2: number, steps: number, currentStep: number, alpha: number): number;
+        static interpolateColor(color1: number, color2: number, steps: number, currentStep: number, alpha?: number): number;
         static interpolateColorWithRGB(color: number, r: number, g: number, b: number, steps: number, currentStep: number): number;
         static interpolateRGB(r1: number, g1: number, b1: number, r2: number, g2: number, b2: number, steps: number, currentStep: number): number;
         static packPixel(r: number, g: number, b: number, a: number): number;