Enhance @silent functionality for DMs and pings to use a different notification colour than red

The addition of @silent pings has been great for alleviating fears around being annoying and social anxiety over sending little things to friends.

However, on Desktop you can only differentiate @silent pings from serious ones by having sound on.

It should be possible to convey to a friend that, “Hey - I found a silly little thing that I want to share with you” and that the ping/DM they received is not an “important one.” Conversely, you can then convey “hey, I want you to read this now” by not using the silent ping feature.

As such, normal DMs/Pings should remain red. Silent pings should be orange or green even.