Why does the red color channel lose the most details during jpeg compression I have an e-commerce website dealing with flowers and cakes. We get our photoshoot done inhouse and also the post-shoot editing of images. While we upload them on the website all images go through the same image compression algorithm. But if we compare all images, then we find product images having red color in them loosing out most of its details only in the areas with red color. 

I have attached an image below for your reference, here the left-hand side image is at 80% quality and the right side has no compression in place. If you compare all these images, then you will see that the red-colored areas of the images lose the most details, at least visually. 

I have read about jpeg compression but it says that color doesn't make any difference, but it is not the case here. 

Can we do anything during photoshoot or post-editing to fix these issues?
One issue is "chroma subsampling". The image data of a JPEG is not stored in packed RGB but YCbCr as 3 seperate planes. The Cr and Cb channels contain colour information and the Y channel is luminance. In JPEG it is common to use a lower resolution Cr/Cb channel, typically at half the resolution of the Y channel, this is know as 422 Chroma subsampling (another variant is 420 where only the horizontal resolution is halved).

What you can do is select 444 Chroma subsampling, if possible, which will mean no down-scaling of the Cr/Cb channels. 

In Gimp you can select the subsampling type in "advanced options" when exporting JPEG files. This is independent of the quality setting slider.

There is a great image from wikipedia which compares the various subsampling modes side-by-side with a visualisation of one of the chroma channels, you can see the red decal in the centre is most affected by downscaling as that channel has high contrast edges



Wikipedia article for Chroma Subsampling