If I may offer one viewpoint on this.
There are several steps that may, or may not, be involved in Tartan design.
1) The Design
Anyone can, and may, create a design for a Tartan. There are on-line Tartan designer programs and some are free (Just be sure to read the fine print). Some people have created hundreds of designs.
What makes a design a Tartan, and what makes a design pleasing may be two totally different things.
2) Listing a Design
In 2009 the Archives of Scotland established "The Scottish Register of Tartan". This is now the 'official' place to list a new design.
Before the Register you would list your design on "The Scottish Tartans Authority".
Listing a Design, while called Registering, does not make it 'official' but simply says that your design - a. Is not copy of an existing design and - b. It conforms to the naming conventions.
For example - When I listed my "Victoria, City of Gardens" Tartan, I had to send in a copy of a document from the City Council of Victoria, BC authorizing the use of the name of the city. Otherwise I would have had to call it simply "City of Gardens".
3) Making a Design "Official"
Again, using the "Victoria, City of Gardens" Tartan as an example. I had to submit a copy from the Victoria City Council showing that they had adopted the design as the 'Official' Tartan of the city.
In the case of a Clan Tartan you would usually seek the approval of the Clan Chief.
In the case of a non Clan Tartan the head or governing body would be who would proclaim the design 'Official'. The "official" US State Tartans have been adopted by the State Legislatures.
4) Protecting a Design
After the Tartan is designed you may wish to protect your design by applying for a Copyright.
5) Have fabric woven in your Design
After all this, you may wish to have fabric woven in your design.
You contact one of the weaving mills and commission a custom run of fabric.
Now, to your design.
It is a common misconception that a "Dress" Tartan is "Dressier" or more formal. While there are some Dress Tartans that are different from the non-dress versions, the most common use of the word is normally just the same Tartan where one of the background colors is replaced with white to create a lighter, more feminine design, "More like a ladies dress".
For example
The MacKenzie/Seaforth Tartan, Modern Colorway.

The MacKenzie/Seaforth Tartan, Modern Colorway, Dress Version.

The Black Watch Tartan, Modern Colorway.

The Black Watch Tartan, Modern Colorway, Dress Version.

The Royal Stewart Tartan, Modern Colorway.

The Royal Stewart Tartan, Modern Colorway, Dress Version.

What I hope you can see from these examples is that the "dress' versions are easily recognizable as the same Tartan. Just one of the background colors has been changed to white.
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