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Outside, with the sun shining on it, I would think a darker solution would adsorb sunlight more efficiently and would get warmer and hence evaporate more rapidly than a colorless liquid. Inside I'm not sure there would be much difference. This is where Science comes in -- don't look for opinions, do an experiment yourself. Here is an easy way, no sophisticated equipment needed: get a pencil, a short board and two cups, one with water the other with old coffee. Let them sit overnight to equilibrate the temperatures. Sit the cups on the board, balance the board on the pencil. See which way the board tilts if one evaporates faster than the other. A Science Fair project!!

Hm... I would tend to think that it depends on what you used as colourant...

If you used a volatile liquid, the evaporation rate would appear faster...

If you used a viscous liquid, the evaporation rate would appear slower...

If you now use something that will somehow bind with water molecules (through hydrogen bonding for example), the evaporation rate will appear slower again...

I think the colorant should be in low concentration or we shouldn't refer to the solution as "water". The emphasis in this question should be only the color. Other physical property changes should be minimized in a good experiment.
I think you [/I]CANNOT[I] have a dark colored, volatile liquid. You could dissolve a dark pigment in a volatile liquid but that's not fair -- of course it will evaporate faster.
The same considerations go with viscosity modificatons; they are affecting more than just the color.
Of course you could add the UNCOLORED solvent and see how it compares with the colored version. That would be fair and we could extrapolate the results to a theoretical "pure" water.

As you said, only experiments will tell us :)