How to increase RGB values of a radial gradient of shapes every 1 or 3 frames?

Hello everybody. I really need help. Indeed, i would like to inrease the RGB values of my radial gradient of my shape every 1 or 3 frames. I did it manually, but its very long. So i would like to know if anyone can help me to make it with code, it's will be most efficient and fast. I've already created my shape with a radial gradient. Now i would like just to increase the RGB values of my radial gradient. Can you help me please!

This code create my shape with a radial gradient:

var radType:String = GradientType.RADIAL;

var radMatrix:Matrix = new Matrix();

radMatrix.createGradientBox(120,120);

var tabCouleurs:Array = [0xFFFFFF, 0xAEAEAE];

var radColours:Array = tabCouleurs;

var radAlphas:Array = [1, 1];

var radRatios:Array = [0, 255];

var gradients:Sprite = new Sprite();

gradients.graphics.beginGradientFill(radType, radColours, radAlphas, radRatios,radMatrix);

gradients.graphics.drawRect(0, 0, 120, 120);

gradients.x = 50;

gradients.y = 50;

addChild(gradients);