Well, I thought it meant that every tube of that particular paint was of the same consistency and colour and you would never have any problem to match it if you were using more than one tube for a large painting.
Not really - it actually refers to the the lightfastness of the paint. Watercolour medium as other mediums over time may change colours due to light sensitivity. Depending on the organic or particulate size of the materials in the paint - they can have a more or less "fugitive" quality.
Take for example - Alizarin Crimson - over a number of years, it may change its colour especially if it has sunlight shining on it and the glass does not have any UV protection when sitting over it. However, "Permanent" Alizarin Crimson has a slightly different set of properties which makes the paint longer lasting when its on the watercolour paper.
The best thing is to try the colours out and not be concerned between their lightfastness. The most important is to be creative and as your practise grows you may wish to take these types of concerns more seriously. Its another learning aspect of painting and will help to strengthen your understanding of how the paint reacts to the paper and the water.
My next show will be June 5th and I will be at Heritage Hall 3102 Main Street. 11-6pm I will have my watercolours, colouring pages, cards and a few prints, please joing myself and 16 other artists in a great event with a terrific variety of styles and mediums.