Any help would be appreciated.
End of quote
Well you can use the chart I posted above. That will tell you the area of influence even if you can't see the circle.
As far as not being able to see the circle AFAIK there aren't any options to turn it off. I have heard of issues with this when selecting custom colors but I think that was when someone selected black as their race color, a particularly poor choice of colors. Other than that I have no clue as to why you aren't seeing a influence area.
However, trade routes are unaffected by running through the area of influence of a resource mining SB regardless of the resource that is being mined. Trade routes are only affected by economic starbases *not* resource mining starbases that happen to be mining an economic resource. Also the economic SB must have a trade module installed to affect trade as well. AFAIK there are three different trade modules that can be installed on an economic SB; Trading Post (Trade+10%), Advanced Trading Post (Trade+20%) and Trade Center (Trade+30%). You need to have the required tech for the module (Trade, Advanced Trade, Master Trade) as well as the lower module installed to add the next module.
However the fact that your attempting to use a mining starbase incorrectly has no bearing on being able to see it's area of influence, it still should be visible when the SB is selected.