The word former refers to state. It means that the person or object was something, but no longer is. The word "former" only refers to sequence in special cases where it is contrasted with the word "latter" (in which it means the first of two given items).
The word previous refers to sequence. It means that the person or object was/did something before something else took over or replaced it. As StoneyB rightly clarifies in his comment, "the previous" means the directly preceding member in a series, however "a previous" can refer to any earlier member in the series.
The word last, in this context, means the same as "previous", but is only used to refer to the immediately preceding item. (Jay warns that "last" can be ambiguous as it is also used to refer to the final entry in a series.)
Thus, you can say "former coworker" of someone who is no longer a coworker. However, the word "previous" means the one before the current, so saying "previous coworker" or "last coworker" does not make sense unless you had a coworker and they were replaced.
Referring to TV series, you can say that you preferred the "previous" or "last" show, and this would refer to the show immediately preceding the current show. You cannot say the "former" show in this context.
When referring to a show that aired earlier than the immediate previous, you can say "a previous show". Otherwise, you can be more specific. Depending on the circumstances, you might say "the first show", or "one of the earlier shows", or "episode ten", or simply "one of the older shows". You could even say something like "five episodes earlier".
In the first part, I would say:
Glasses suit you.
though it would be more natural to say:
Glasses look good on you.
Glasses should be treated as a mass noun, since you are not pointing out a specific kind. So no article is used. And suit is better than fit, since fit has more to do with size.
In the second part, I would say:
I think you should go for the blue one. It suits you because your eyes are blue too. So they match.
or simpler:
I think you should go for the blue one. It suits you because they match your blue eyes.
Best Answer
It depends on whether you want to focus on the fact they are beautiful, or attention-grabbing and hard to look away from. In the first case you might want glamorous, which once had connotations related to "magical" effects but now mostly means "the sort of appearance you expect from the rich and famous"; this tends to imply that things aren't entirely natural, however, and describing eyes as glamorous might cause some confusion in readers. They would possibly think you meant they were heavily made-up with mascara, eyeliner and eye shadow.
If the intent is that they grab attention and are hard to look away from, mesmerising is a good word choice. It suggests that one looking into the eyes tends to fall into a trance, but no-one would actually take that literally without something else pointing that way. It would usually be taken to mean that you find it hard to look away, that you feel as if you could fall into a trance looking into them.