I am A Sheriffs Deputy and was looking to find a tartan to wear on a formal occasion (a Deputies Wedding) the outfit would consist of our Department Dress Coat, a Campaign Cover, Shirt and tie. I was thinking of going kilted. I already have the approval of my sheriff. The question now becomes what tartan. I have seen Sheriffs Dept Pipe Band wearing kitls with a brown tartan but I cant seem to find a Sheriff's Tartan I can find the general Law Enforcement one but not this brown one I keep seeing.

Question before you go any further - is the uniform jacket the right length for a kilt? Dressy kilt jackets are significantly shorter than most Saxon jackets.

One possibility is the light conditions during the photo which - sometimes- can make some colours look different. I found one photo of Law Enforcement that might be seen as 'brown'

Or, perhaps the tartan you've seen is State or some other. Tracking down the Sherriff pipe band and asking might be your better option.

Father Bill makes good point

Is there any chance that there is a photo of the Pipe Band in question? Maybe we can identify it for you.
Or perhaps the name of the pipe band or a link to the bands site or facbook page.

Afghanistan Memorial tartan is nearly sheriff brown. J Higgins shows it as a tartan they could make a kilt from. I. really like the tartan and may someday have a kilt made of it myself.

Locally here in Orange County California we have the AOCDS Pipe Band who wear a tartan they designed.

It's very nice, the ground-colour being the green of their uniform shirts, and with orange stripes of course!

But of course that tartan is specific to that agency.

Here, a piper and the Drum Major

https://i.imgur.com/VUsjlAb.jpg