Obviously I wanted to use the universally accepted colors for the flight categories;

• Green - VFR
• Blue - MVFR
• Red - IFR
• Violet - LIFR

Then to depict weather conditions I chose colors that I thought would best represent the weather. In fact, to amplify that the color was depicting a weather condition and not a flight category I used 2 colors to represent a blink. 

The best part of this, is the colors are changeable to the builder's preference. So if you believe using Blue to represent rain is not optimal, then feel free to change it to what you believe would be better.

To answer your questions, MVFR with rain would be solid blue then blink blue. And if fog is reported, but the FAA is reporting a VFR flight category, then yes, the airport will show a solid green then blink silver/grey. This is all dictated by the metar reported by the FAA.

You can change the colors to whatever you feel is best. The other option is to turn off the individual weather conditions and only display the Flight Category color. 

Below is the categories of weather conditions as reported by the FAA. You can visit https://www.aviationweather.gov/metar/symbol  to decode each of these. - Mark

#Thunderstorm and lightning
wx_lghtn_ck = ["TS", "TSRA", "TSGR", "+TSRA", "TSRG", "FC", "SQ", "VCTS", "VCTSRA", "VCTSDZ", "LTG"]
#Snow in various forms
wx_snow_ck = ["BLSN", "DRSN", "-RASN", "RASN", "+RASN", "-SN", "SN", "+SN", "SG", "IC", "PE", "PL", "-SHRASN", "SHRASN", "+SHRASN", $
#Rain in various forms
wx_rain_ck = ["-DZ", "DZ", "+DZ", "-DZRA", "DZRA", "-RA", "RA", "+RA", "-SHRA", "SHRA", "+SHRA", "VIRGA", "VCSH"]
#Freezing Rain
wx_frrain_ck = ["-FZDZ", "FZDZ", "+FZDZ", "-FZRA", "FZRA", "+FZRA"]
#Dust Sand and/or Ash
wx_dustsandash_ck = ["DU", "SA", "HZ", "FU", "VA", "BLDU", "BLSA", "PO", "VCSS", "SS", "+SS",]
#Fog
wx_fog_ck = ["BR", "MIFG", "VCFG", "BCFG", "PRFG", "FG", "FZFG"]

@markyharrisok, thanks!

I’ll continue to play with this 

I found a more satisfying mix of colors to show rain. A slight variation on the blue your default is. As it stands if it MVFR the only real color change noticed is the light blue as the dark blue is the same as MVFR blue. So it was a light flash of color and back to blue. So I did the same light blue, then a slighter darker blue, then the DARK blue for MVFR. Those show up great and is distinctive. Having this ability to add info by the flashes is great!