How to fix gray background on images without checking "retain color depth"

I have a cover page on my report where the user can insert a logo image. The problem is that if the logo image has a white background it will turn the white background gray. I have figured out how to resolve this by checking "retain original image color depth.u201D The problem with this is that all the images in my report are larger so the report pdf file size goes from 3mb to 30mb. Is there a way to make the logo image appear as normal without having to check the retain color depth? I have tried adjusting the image in photoshop several different ways but havenu2019t figured it out yet.