French Marigold Germination

None of the seeds I took from my bronze-coloured French marigold plants from last year germinated this spring (nearly 200 peat pellets). On the other hand, I had no problem germinating the seeds from the yellow-coloured marigolds. I had purchased the original seeds (mixed) the year before from Richters; these produced the two colours and the plants were exceptional. All source plants were neighbours to each other in my back garden, were sown in the peat pellets the same way, at the same time, and kept under the same temperatures and conditions. I even re-sowed more bronze seeds after three weeks, but still no germination took place.
I am wondering if the seeds from the yellow French marigold plants produce colours other than yellow and if the bronze plants are sterile. I am growing seedlings to raise money for a local development organization in South Asia and some customers would like to know in advance what colour the flowers will be. Many people prefer preference for the bronze colour.

The french marigold we sell is a variety that has been popular for insect control mainly because of its compact size. It is not a variety that has been optimized in any other way for insect control – in fact, it was developed purely for ornamental purposes. In the 1960s it was tested for its insect-repellent effect.
We do not produce the seeds of this variety ourselves. Because this is a variety we do not sell a lot of we rely on an international seed grower for our supply. It has been our impression that the seed is open pollinated and thus should come true from one generation to another. However, the effect you are describing strongly suggests that the variety is in fact a hybrid, with one parent presumably having the bronze flowering trait and being sterile. Normally, when you collect seeds from a hybrid plant they will produce offspring that revert back to the parents to varying degrees. If one of the parents was sterile, then some of the seeds will turn out to be infertile and incapable of germinating.
Unfortunately there is no way of telling the colour or other characteristics of the seedlings in advance.