We changed the colours to a combination which better showed markers and to unify with the online world map. We also recommend your users use the online world map instead of the vector map, because it has much greater accuracy and detail when zoomed in.

There is no instant way of changing this. If you don't need the country fills, you only need to untick Layers > Countries, then visit Map > Colour effects > Base colour and paste in a HEX code or pick a colour manually.