How can I make a color wave effect?

Basically I have a game where the player moves along tiles and must tap when the player is within a target on the tile. When this happens, I want to have a “flash” of white starting from the centre of the tile spreading outwards in all 4 directions until it hits the edge of the cube, where the flash then dissapears. I would like this flash the take the shape of a hollow square, where it’s alpha fades out on the inside edges.

I am still learning Unity so please don’t assume I know even basic things.

You can fake this by making a transparent texture in the shape you want and then put it on a quad with a transparent material. Scale it down to nothing and have it slightly higher than the tile at which it makes the effect above. When you want to trigger the effect, scale up gradual via the Vector3.Lerp() function until it reaches your target size.

Vector3.Lerp(startScale, endScale, scalingTimer);

Try that, if you have troubles, post your code.