I need to cover cakes with fondant in advance and leave in regular home refrigerator for 1-2 days.  

No, fillings are not highly perishable, but I like how sturdy they stay when cold and find it better to continue decorating when cakes are slightly cold and "sturdy" 

Then only reason I want them refrigerated is so they stay cold and firm.

I live in a very humid climate, but run air conditioning.

Given this, what are the best ways to do this so fondant doesn't get ruined?

I am planning on placing the cakes in sealed styrofoam boxes.  Will this be enough?  I've done this before but only kept them in the boxes for a few hours, not overnight.

Also, anyone tried placing a fondant covered cake that has black fondant on it next to a vivid color - did it "bleed"?  Black squares next to bright orange squares going around cake...

Thank you!

idk-- if you place them in sealed foam boxes it will insulate them from the refrigeration no?

and make the warm up to room temp as gradual as possible to minimize the condensation thing--

you mean a black cake stacked with another color? why don't you test the colors next to each other in the fridge and take them into room temp and see how it all goes before you place the cakes--y'know while you are applying the fondant --test it