Add option to not detect greyscale images as similar to originals

[TransparentDuck]

Feature Description

First, thanks for making this tool, it's great.

I'd like the option to not detect greyscale images as being similar to originals. I have greyscale versions of some images, and would like to keep both them and the originals when running a Similar Images comparison.

I've tried using all the built-in algorithms, and none of them seem to do this.

I understand at least some of these algorithms convert the images to greyscale in the background before performing the similarity comparison. Are there any that could be used that don't do this?

Thanks!