UMG - Color Swatches baked into Images

Hello -

I have a set of image assets that I will be using to populate my UMG interface. The assets are country flag images that have been designed in photoshop with color swatches in the corners of the image. Those color swatches should be used to determine the color that sits behind the flag. Attached reference of one of the assets, a breakdown of how the desired result, and a snapshot of my application of the flag in UMG.

While I have achieved the basic design I am looking for on my UMG leaderboard, I have yet to find a way to allow the corner of the flag asset to drive the backplate color behind the USA flag. Thanks in advance for anyone who can help me achieve this.