Pointing Cobbles
 

I have laid a 15x6ft area in the garden with grey cobbles and want to
'dry' point them with a similar colour. I beleive concrete colourants
come in both liquid and powder form but want to point the cobbles dry.
I have seen 'Biofix' but is expensive, can anyone advise what are the
potetial problems of thoughly dry mixing concrete and powder colourant
to use for pointing?