For better visibility, I would suggest 1 pixel wide outlines (constant width at any zoom; outside, around the whole cluster, not inside per tile like self faction color) for different object types, e.g. blue outline color for all resouces and different fill color for each resource type; red outline for all hostile faction, but still repective fill color of that faction, green outline for allies, yellow for exporeable, ... . That would also make sub pixel objects larger to be visible at all (when zooming out far).
