Good for you, Cynthia! You can buy pre-tinted gelcoat readily enough, e.g. at Martin Marine in N Van or Steveston Marine/Hardware in Kitsilano (among others). Any hardener I’ve used has been clear. You’d need the smallest amounts that they sell. No guarantee with that the colour/tint match would be perfect but, for a small gouge, you would never notice if it were not exact. A v small amount of rubbing compound (like for car bodywork) can be used to polish it after, so that it blends well. G’luck!