RetainerBox results wrong color in Mobile

I displayed a same image with two different ways in es2

Left one is with Image.
Right one is with Image with RetainerBox(tested with all blend modes)

As you can see, Rigtt is not correct washed and darker, it is different from what it has to be.

https://github.com/EpicGames/UnrealEngine/pull/3156
I want you to check my pull request.

Hi Varioov,

Your pull request has been logged internally and has been assigned to an engineer for review. Keep in mind that this process may take some time and there is no guarantee that your pull request will be implemented.

Thank you for your contribution!

Ed