I've done this type of repair many times in the past, but I have the advantage of having Moulds to put the grip into to form the repair into the correct shape.
However, I have carried out repairs without the aid of a Mould : To colour the Araldite, I originally used an epoxy colouring agent available from Hobby Shops, but have also used shoepolish. In both cases I experimented with the mix in order to achieve a reasonable approximation of the bulk colour. Use of a colouring agent to the Epoxy generally increases the hardening time, so patience is a must. To get the contour, "Sellotape" or similar can be used to form a crude Mould for the repair area. In my experience the adhesive needs a lot of mixing and needs to be left to "de-gass", otherwise bubbles will appear when the repair is trimmed to shape. I used 24 hour Araldite and applied gentle heat to aid flow into the repair area and minimise air bubble problems. When set I left the grip to harden for a week, or a few hours at elevated temperature in an oven. Then shaped using succesively finer grades of sandpaper, with a final buffering, then polished with a shoe brush laden with shoepolish. The original grip was undercut and drilled to maximise contact area, and in some cases, pinned as well.

Results were good, in a lot of cases, barely noticeable.

HTH, Vic T