[GRASS-user] setting a color value to transparent

Chris Bartolomei surfcjb at yahoo.com
Fri Apr 23 11:19:03 PDT 2021

Good afternoon all,
I have a polygon map with a handful of features, I've added a column I use for setting RGB values "RRR:GGG:BBB" to color them. I use three (3) colors - red, orange, and yellow - but I would like some of them to be transparent but I can't find anywhere in the manuals what the code would be for transparent. Searching Google-land I see there's an RGBa standard which can set tranparency but GRASS doesn't seem to support that. I've tried setting the value to NULL, to "", to "none", and tried "0:0:0:0" (RGBa) all to no avail ... 
I am using ps.map to create an image so the ps rules file tells GRASS to use the RGB column to define the colors ... I believe I'm stuck with this methodology for now.Am I going to have to select the features which I do want colored and make a new map with just those features? or do I have to remove the postscript command for the RGB column and create a color table then reset my category values to 1, 2, 3, or 4 using a color table something like:  nv white  1 red  2 orange  3 yellow  4 white
I was hoping to avoid creating a color table and changing the category values as this map gets modified twice a day... It's running in GRASS 7.4 on Linux ... 
Thanks and happy weekend!:)
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