Hi Aubade,
Well, there's a lot of things to address. I hope it all makes sense. : )
First, if you plant a bunch of different named cultivars of marigolds that are all the same species, you will probably get crosses and your seed that you saved will make babies that look different than the parent. Also if you grew a hybrid cultivar with no other marigolds around to play hanky panky with, you will still have babies different from the seed you saved. You might not care though, and sometimes the babies don't vary too much from the parent.
Second, when saving seed it is best to save seed along the way from blooms from different times. If no pollinators are about and/or the weather is too hot or too cold, you will not get viable seed from the blooms. So it is possible to save seed from the end of the season and have few actually good seed in the dried flower heads.
Third, it is good to put seeds you saved in an envelope. The air tight container is ok, but only after you are sure the seeds are sufficiently dry. Seeds can be ripe on a plant, but there is still tiny amounts of moisture that need to dissipate before they can be put in an airtight environment. I personally don't put in plastic because of this.
Fourth, the same types of seed can be planted at the same time and sprouting times can vary. It can be a week or two difference sometimes. I'm not sure why, but it happens all the time.
Fifth, seed companies do a good(well most of the time) job separating a higher percentage of viable seed from the unviable. They don't treat the seed to germinate better. To get technical, there's a few seeds they do prep for better germination, but in most cases like the marigolds they've done nothing to the seed.
You may still get sprouts, or you may not. If you don't, hopefully you figure out what happened and you correct that mistake this year.
Remy

That is very helpful info, thanks!
Hopefully they'll still sprout...

So the seeds I saved never sprouted. :-(
I decided I might as well try soaking and pre-sprouting the rest of them I saved, to see if any will grow.

But I'm wondering what will happen since the 3 different colors weren't separated. They were all Tagetes tenuifolia, but yellow, red and tangerine. So does that mean new plants from the seeds I saved would be one of these colors or some combination of them?

Hi Aubade,
I don't know dominant traits of Tagetes tenuifolia, but the seedlings would probably be heavy on a specific color. You could get all kinds of possible combos of those colors though.
Remy