I am making a fondant covered cake with fondant trim and lettering, all in different bright colors, ie. yellow, pink, blue, green. My question is if I do this today for delivery tomorrow will the darker colors bleed onto the lighter colors.  I am doing lettering in yellow on top of the bright pink. Appreciate any advice.

I did a bright pink and purple cake with white lettering last year and was worried about the same thing I completed it the night before, boxed it up and left it on the counter (i was scared putting it in the fridge would make the colors run) and the letter were still bright white by morning! :)

Put the finished cake in a cardboard box, then put that in the fridge.  Unless you have a fridge with really high humidity, it will be fine.  The box rather than the cake will absorb the moisture.

Thanks! I really appreciate your advice.

A fondant OR b'cream iced cake will be fine sitting out at room temp overnight:)

It is best not to put them into the frig unless there is a filling used that must be refrigerated.

If it *must* be friged, the box it in a cake box, then put that into a plastic bag in the frig.  At least 1 hour before delivery or p/u frmove from frig but leave pkged. 

I refrigerate my fondant cakes all the time, regardless if the filling is perishable.  A cold cake is much more stable to transport than a room temperature cake.  Never had a problem, but it does depend on your fridge.  If you have time, test it by putting a cupcake with fondant or some cake scraps covered with fondant in a cardboard box for a few hours.  When you take it out, you may see a little condensation, just don't touch it and it should dry fine.  If there is a lot of condensation, then you'll know your fridge humidity is too high for a fondant cake.