I'm in the same boat, and it's been a problem for quite a while now. The best option is to use the Huawei camera app in Pro mode to get photos in raw mode/DNG. Make sure the Raw is selected in settings though. (In Pro mode.)
I personally think the Adobe camera app is defaulting to the B&W camera on the Hauwei (as Huawei has three lenses and one lens is only monochrome) and unfortunately, this can't be changed in Lightroom, as there is no colour information in the actual DNG file. When this will be fixed is anybody's guess.
A
Anonymous
November 5, 2019
Hi all,
I can confirm exactly the same behaviour with the P20 Pro on EMUI 9.1. Lightroom App is Version 5.0, Nov 3, 2019. This is using Pro or Auto Mode, and either DNG or Jpeg. Front camera works in color, but that is n ot the point here. App is unusable at this point in time.