I think the “dullness” comes from HDR photos conversion to SDR. It is hard to deal with, since not all devices are capable of rendering HDR. The best advice I can give is to use Edit function on your phone and to bump contrast before uploading 🐶🐾🫡
Discussion
Something like this! 🐶🐾🫡 
Gorgeous!!
It’s odd cuz when I go on other nostr apps the photo has more colour, less dullness just like how it looks in my phone.
Seems to be only on damus for me.
Ah, then it maybe due to the optimization to reduce the size. Let me check on that and see what I can do 🐶🐾🫡
Ok, I made some changes, let’s see if it helps! 🐶🐾🫡(unmodified from your original upload) 
Looks the same as when I posted it and duller than when shot or saved in my phone.
Ok, then it’s definitely HDR thing. One suggestion, as I said, is to edit the image before the upload and bump contrast and saturation 🐶🐾🫡
Thanks for trying 🫂💜
Try to check again with different pics and let me know if the colors match your expectations. Thanks a lot for spotting it and letting me know! 🐶🐾🫂💜🙏🏻🙇♂️