(this should be a comment, but my reputation is too low)
Setting jpeg_quality will not disable compression because it does not disable processing. JPEGs will be always compressed, and they are almost never lossless, not even at 100 – it does not stand for “100% original quality”.
What happens here, is that WordPress’s default image processing does not respect color profiles, just as @Bigue Nique says.
To add some insight: WP ignores color profiles from the images and the browser sees them as unprofiled/sRGB. The loss of saturation is a typical artifact when the AdobeRGB profile is stripped.
As a photography student I had made that mistake for years (luckily, my pictures were usally grey ;).
It still makes sense to shoot and use AdobeRGB, or other color profiles, just make sure to convert to sRGB (important: convert to profile, not apply profile) at the very last step of your workflow. You can then even strip the potentially embedded sRGB profile and thus make the image unprofiled, since it does not make a difference in appearance – this is what image size optimizers do to save a couple of bytes.
I’m sure there are plugins to do the profile conversions automatically, but it is good practice to be aware of color profile issues when you publish to the web (say, forums or customers who don’t have that plugin).
@Nina Marie – please mark an answer (Bigue Nique’s) as the correct one.