By default, Firefox will try to color manage tagged images (JPEGs and PNGs). You can review and experiment with the following preferences to see whether one of them is causing the problem:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste gfx.c and pause while the list is filtered

gfx.color_management.mode - governs application of color management to images

0 = off 1 = on for ALL images 2 = on for TAGGED images (default)

I can't recall whether you need to quit/restart Firefox before this change, or changes to the below preferences, takes effect.

I think the following are only relevant if you have profiled your monitor (e.g., pro photographer).

gfx.color_management.display_profile - if you have created a custom monitor profile and Firefox is not using it, you can enter the path to it here.

gfx.color_management.enablev4 - double-click to toggle to true if your custom monitor profile is an ICC v4 profile

gfx.color_management.rendering_intent - whether Firefox honors or overrides the intent flag in the ICC profile, by default, overrides to Perceptual