Create a color gradient animation

Hi everyone!, I'm currently developing a mobile game based on the music, which uses color animations as visual alerts to advise the player of the future notes that he's gonna need to press. On the current version I'm using a gradient transition to show that a determined note has to be pressed soon(I would share with you the time values of the animation for sure, also let you know the color value according to the time function). So it would be the same idea as I use now , but right now the animation paint with a determnied color all the pad(square or note) area, since the animation begin, and that's pretty uselles for advise the player properly. What I want, is make the animation as the color was growing up on the square area, and that when the player time to press comes, the color would fit all the square area. I haven't been able to create any video demostration or word explanation, but I saw on a game the effect that I need for my game. Here's : [login to view URL] Check it on the min 8:57, there you will see on the right under corner "smoke density", there you would see what I was talking about here, but It would not be exactly the same as appears on the video, because on the video the color value is always the same and also I need the opposite effect,The color must expand occupying the entire area, there is no contraction until disappearing. So this would be all I guess, that effect but with my own request and with 3 colors types according to the notes types that already exist in the [login to view URL]'s my game beta gameplay: [login to view URL] The project budget is currently 120 $. Thanks for have read the entire post, have a good day.