Yes I suppose we must agree to disagree. I too have been an artist by profession my entire life.

My point was that, as far as we know, tartan designers in the old days picked colours they fancied.

This notion of having your starting point being the meaning some individual applies to a certain colour, I think, is quite recent.

Colour is colour, it is abstract, it is a result of the laws of physics. Colours have no inherent meaning. (An example is how one culture might see the colour of death and mourning being black, another culture white. Black and white themselves are simply colours and have nothing to do with death.)

It's usually, in my experience, been non-artists who want to create a design by starting out with non-artistic considerations.

An example is the field of logo design. I see logos every day being used by small companies that were obviously designed in accordance to the "specs" laid down by the company owner. People who own companies, especially smaller companies, always seem to want a picture of whatever their company makes or does as part of their logo. It's the bigger companies who "get it", who realise that an effective design makes an effective logo. In other words, the best logos are designed from an artistic standpoint, not the standpoint of non-artistic considerations like making a picture of something.

Mecedes' logo isn't a picture of a car, it's a simple strong design.

So in the back of my mind I think "here we go again" when somebody has a tartan and they say "the blue stands for the sky over Montana (or the sea around Hawaii or a baboon's butt or whatever). Blue is blue. Does it look effective in that particular design or not?