- Are your pictures in your Photos app affected at all that are not associated with Snap?
- Is this only when using SnapChat or its website?
For Snap, you may want to look more closely at the updates they have made to that app that have nothing to do with iOS updates. Snap has had 14 updates to their app in just the last month with the most recent one being 4 days ago. Any of these updates can change the behavior of the app and even introduce bugs that would need to be resolved by Snap. You can certainly use Snap Support for any issue related specifically to that app. Server side settings for snap on your account will also affect those viewed on their website.
https://help.snapchat.com/hc/en-us
For an issue that is not Snap related, post a screenshot of what you are seeing as there are settings on your device that will affect colors, but will not be specific to a single app/website.