Image from transparent to white

Hi,

I'm tring to create an image using color from transparent to white without any background. I want to use that image in an application where the user select a color and the fadding creates a nice effect with any color (because the image has a color from transparent to white so if the user select blue then image will appear from blue to white and so on). I can't seem able to do that in Photoshop (tried with gif and png). The result gives me a white image whithout any transparancy. Is that possible to do?

Thanks!

What do you mean by an application? Do you mean a window application, like something made from C++ or something online based?