You can colour code the pushpins automatically if you use the displaydatamap method (see the help for details). Alternatively, you can manually (in code) adjust the pushpin's symbol.ID based on some criteria. All this assumes that the field containing the value to be used for colour coding has been imported (or at least available for manual option)

AFAIK the backgound map is a single layer and unamendable. The best you can do is turn off all the all members of the placecategories collection.
You may want to try changing the style of map displayed (ActiveMap.MapStyle). The options are limited but there may be one better suited to your needs.

M.