How do I make a fading decal?

How do you make a decal fade, from a color to another color? Like, A White decal that fades from like orange to blue or something of the matter, I'd like it to change in a rainbow pattern like any color, it turns from One Color, to Another, how would you do that? Could someone demonstrate me, by giving out an example? This is what I have so far, I used the Image label method, but, I want to add a nice fade effect so it doesn't just change color with some choppy effect.

while true do
x = (math.random(0, 10) * .1)
y = (math.random(0, 10) * .1)
z = (math.random(0, 10) * .1)
script.Parent.ImageColor3 = Color3.new(x, y, z)

end 

Well, there's a few ways to do this. But you'll need the different colors made and uploaded to start. Once you have those make the decal and insert a serverscript into it with the following code:

decal = script.Parent
colors = {(123), (234), (345)} -- Put the decal id's here. Change the numbers to the id's.

texture = 1
while true do
decal.TextureId = ("http://www.roblox.com/asset/?id="..colors[texture]) -- This makes the TextureId into w/e number texture is equal to in the table.
texture = texture + 1
if texture >= 3 then -- Change 3 to the number of colors in the table.
texture = 1
end
wait(1) -- Change to how long you want the color to exist.
end