In the British Army, the Canadian Army and most of the other Commonwealth countries the hackle is worn by some infantry regiments, especially those designated fusilier regiments and those with Scottish and Northern Irish origins. It was commonly attached to the feather bonnet worn by Highland regiments (now usually only worn by drummers, pipers and bandsmen). The colour of the hackle varies from regiment to regiment.

In the British Army, there is a single regiment of fusiliers, plus a battalion of a large regiment:

* Royal Regiment of Fusiliers: Red over white
* Royal Highland Fusiliers (a battalion of the Royal Regiment of Scotland): White

Following the amalgamation of the regiments of the Scottish Division to form The Royal Regiment of Scotland on 28 March 2006, the following hackles are being worn by the regiment's constituent battalions:

* Royal Scots Borderers (1 SCOTS): Black
* Royal Highland Fusiliers (2 SCOTS): White
* Black Watch (3 SCOTS): Red
* The Highlanders (4 SCOTS): Blue
* Argyll and Sutherland Highlanders (5 SCOTS): Green

There are also several fusilier regiments in the Canadian Army which wear the hackle:

* Princess Louise Fusiliers: French grey
* Royal Highland Fusiliers of Canada: White

Scottish-influenced non-fusilier regiments which wear the hackle include:

* Argyll and Sutherland Highlanders of Canada (drummers on feather bonnet only): White
* Black Watch of Canada: Red
* Calgary Highlanders (drummers on feather bonnet only): White [2]
* Cameron Highlanders of Ottawa: Royal blue
* Canadian Scottish Regiment (drummers on feather bonnet only): White
* Essex and Kent Scottish Regiment (feather bonnet only): White
* Lorne Scots: Primrose yellow
* Queen's Own Cameron Highlanders of Canada: Royal blue (except pipers in full dress, who wear an eagle feather instead).[3]
* Seaforth Highlanders of Canada (drummers on feather bonnet only): White

Irish-influenced non-fusilier regiments which wear the hackle (on the caubeen) include:

* 2nd Battalion, Irish Regiment of Canada: Green (light blue for senior NCOs and officers)

I hope this helps.

Cheers!

Paul