So why do we darken our horses points ? I'm not really sure on why just that most horses look better and "finished"
Bay horses with black points often have a bit of brown hair in the black points and this looks better blackened out, Chestnuts look better because it seems to break up the colour.
If you choose to darken your horses points try not to use a leather dye, there are a lot of different companies that put out products specifically for this job.
On a brown or bay with black points you would obviously use black but what about chestnuts ? I use a brown on them as black is way to harsh an obvious.
It should never be noticeable, it should look natural, the key to this like most things with horses is blending, I use a cloth to apply , put on a little first then add more till you get the colour you're after and then I blend.
The photo of the little pinto is a before and after, I used black on her.