It actually doesn't honor your System Settings wallpaper, you probably just set it to "Ventura Graphic" so it appears to match. But it is always Ventura Graphic, because this setting loads from the sealed system snapshot before the data volume is decrypted at all.
There are three distinct "login screens" in macOS now.
1) Initial login after a restart or shutdown (disk fully encrypted)
2) Login screen after an initial login has occurred
3) The lock screen
1 and 2 are part of the sealed snapshot that is not user changeable. It is determined by Apple. After the update to Ventura, all Macs now display the orange Ventura graphic (except, perhaps, new ones—they may get a special screen as designated by Apple the same way you had Chrome Red/Blue previously). Chrome Red/Blue still appear if you log out (after an initial login) or if you go to change users. The lock screen will display your normal wallpaper.
Why Chroma Red/Blue appear at all is a bit of a mystery. That may well be a "bug" in that it was an oversight. This should probably be the same Ventura Graphic that is present in #1. In either case, it is the same cause—it is the file that loads by default from the sealed system snapshot.