Kills, Death and Capture Notices.
The background.
There are two methods you can use here, the first is editing the ClientScheme.res file and the other is editing the HudLayout.res file (dod\scripts).
1st method...
Getting rid of the Background completely.
To clear the death notice background, look for this group around the top of the ClientScheme.res file…
"HudBackground" "123 110 59 184"
"HudBackgroundActive" "240 207 78 117"
"HudBackgroundUnusable" "192 28 0 140"
"HudBackgroundActiveSolid" "240 207 78 180"
Change.. "HudBackgroundActiveSolid" "0 0 0 0"
The death notices will no longer have any background at all, again adjusting the ClientScheme.res file may not be what you want... because it will affect other areas in the HUD that refer back to this "colour".