when it cures the colour sometimes seems darker than it is. It can often take a few weeks for the water to evaporate and the true colour and texture comes through

You can smooth the top by turning the "couple" up side down on a piece of old concrete and rub it in a circular pattern. Do NOT use your good concrete sidewalk as the rubbing will wreck your sidewalk/patio. You can use a small piece of concrete or rough brick held in your hand but you won't get an even surface. If you use a hand held tool you will also get an uneven surface plus the cement dust is not something you want to get inside a dremel or yourself. It is so much easier to smooth the top while the mix is still wet.
You should have sand in your recipe. Depending on the Peat moss it could be dark in color and aging will lighten.