I have heard of people using african violets in terrariums before. There are a couple things to keep in mind when using them. First, be very careful with watering. Too much water will rot the roots. Second, don't let leaves touch moist soil for a long period of time. These will rot as well. Typically, violets described as blue have a touch of red in them giving them a somewhat purple appearance. All this being said, there's no reason a violet can't be grown in a terrarium, and with many thousand varieties to choose from, there's sure to be one you'll really like. I've included a link to the African Violet Society of America photo page. Just click on a letter and then submit to see different hybrids beginning with that letter.

Here is a link that might be useful: AVSA violet photos

The micro mini's grow fantastic in terrariums. I have several "Fruit Fly", "Teeny Bopper" and "Hot Pink Bells" growing this way.
Key is the soil mix needs a fair amount of perlite in it,,,so porous,,,and the soil should be damp and not soggy wet.
I've also found the double dip sundae containers with a lid work great to root leaves in as well as to grow a micro plant.,,,Debbie

Rob's Twinkle Blue and Rob's Vodoo Blue are great micro minis for the terrariums. They can be delicate however. Tiny Moon Goddess is one of my fav's. It is blue also.

Best of luck to You. You may need it.

Thom