I just recieved a leather back chinch in the mail and it is lighter then my saddle. It looked the same color as my saddle on the iternet. I used neatsfoot oil but it is still not dark enouth. Any help would be great.
You wouldn't have a picture of both your saddle and new back cinch that you could post?
If you rub mor oil into your new cinch it should darken it but make sure to put it on in medium to light coats and give it lots of time to absorb and even out. When you first put it on it might look a bit blochey but if you just put it out in the sun it will even out considerably. Patience and time is the key so you don't over do it. I have wrecked more than a few project by putting way to much oil on to quickly when I am finishing my projects.
How many times have you oiled your cinch? Okay, now how many times have you oiled your saddle?
Oiling is just adding moisture to the leather, which darkens the leather considerably. But as it dries, it will lighten up again. My saddle is Havanna brown, but after 35 years of oiling and use, it looks almost black. Give it time, and keep oiling. Eventually, the cinch will catch up to the saddle.
There are products out there to use to darken leather, I would call Tandys Leather Factory or Springfield Leather and see what they have to recommend. You could even use an oil based dye or stain to artificially darken it too, but unless you know how to cut the dyes or stains, I don't recommend it (especially after it has been oiled).
Oil will treat the leather, but as pointed out, it will take time to make a lasting color change. I find a boot polish that matches or comes very close. I treat it just like I do my saddle when treating scratches and scuffs after riding through thick woods.