I think that is just a gradient used during Normal drive mode. Other drive modes use different color schemes.
I did notice there is a white to red gradient going on from 55-60 on your picture. Wondering if that is just a color scheme for it getting close to the set cruise speed or if it is indicating it is above the 55MPH seen by the Speed Limit reader. I'll have to look next time I set cruise and am accidently above the speed limit....
I know in Baja Mode the "analog" part goes away and only the number shows (for speed). In Sport everything is greyscale-ish. Not sure about other modes. I didn't pay much attention in off-road or rock crawl modes. I haven't used Tow or Slippery yet