They're not doing science with photoshop. They're creating assets for consumption by the public.
Eh, it's been pretty tested. Any person can easily apply filters and verify the change in image properties and see how filters behave.
Why would they worry about that? These colored images aren't used for science, they're meant for marketing.
The filters used are just simple compositions -- making monochrome images colored and adding them together, so that scientists can distinguish different types of gas and dust via color coding.