I have a water tank made out of cement rings that I'm just about to paint.

At the base of the tank is a couple of square meters of concrete which I would like to colour some how,

Whats the best way to do this,paint,stain,,e.c.t.

Also the verges of the concrete are all jagged,if I straightened them out by putting down more concrete would the new concrete bond with the old.

It's just a rough job,it doesn't have to look sharp.I just hate the sight of discolored old concrete

Clean, prime, and paint with whatever color you want. If you want it to look better, get a local guy to smooth it out - shouldn't be hard to find - and before you do the color. If that, then you will need to wait a while for the cement to cure properly.

Is cleaning with a wire brush and water enough.

What kind of primer and what kind of paint.

Does it have to be floor paint.

I can touch up the concrete I just need to know weather

any concrete I add will bond with the old.

Clean to the point where there is no dirt, mold, or other residue on the concrete. Look for exterior paints and go with something that makes sense for your application. If you're just filling some holes and cracks, you might consider a filler Otherwise, for concrete you pretty much have to go with whoever does it decides to do.

prep with wire brush and bleach. Let bleach remain overnight to do its thing. Next day--scrub again and rinse.

Locate some weak hydrochloric acid (know as muriatic acid) from pool supply play.

YES....use safety goggles, gloves and set up a fan for ventilation.

Rinse well.

Most cementatious based pigments are designed to me added to a white portland cement. As about for a pool finisher.

You will need two tradesman to pull this job off successfully: lead blade and a helper to keep him fed with material. The helpers also cannot vary his color batches.

Keep damp for 7 days by "misting lightly" with a water hose...no direct jet of water.

Have fun!