When we think of African violet blooms, we think of first of purple. We might be familiar with pink, white, or even multicolor flowers with stripes, edges, or fantasy markings. Among all these more usual colors, a growing number of green-tinged hybrids have captured our hearts. Some enthusiasts make a point of collecting African violets with green-accented blooms.
Green is an uncommon color for African violet blooms. More than 800 of the well over 3000 registered cultivars have some green in their bloom description. For many of these, however, the green is only an occasional hint of color accenting the edge of the petals. Like fantasy markings, green can come and go, being more present during one bloom cycle and entirely absent in the next.
Light may play a role in the amount of green in the blooms. I've seen suggestions that less light promotes green blooms, as the plant tries to increase its chlorophyll content in order to make the most of the light available. I've also seen suggestions that brighter light means more chlorophyll production for greener blooms. All I can say is, if your violet isn't blooming as green as you think it should be -- move it to where it will get a different amount of light.
As you might expect, a number of green-blooming African violets have Irish names, such as 'Wild Irish Rose', 'Buckeye Leprechaun Charm', and 'Bud's Irish Eyes'. 'Petite Blarney' and 'Lil Bit ‘o Irish' are two of my favorite miniatures (see photos). S. Sorano has registered an entire series with names starting with "Irish," such as 'Irish Cream', 'Irish Mint', and 'Irish Laugher' (see photo). His ‘Irish Flirt' is a personal favorite, with its rose-like double blooms and bright green leaves. It's also known for blooming as a very young plantlet, sometimes producing a bloom or two while still attached to the mother leaf.
Optimara's "space baby" series of violets tend to have ruffled edges on their blooms, often tinged with green. They got their nickname because they were developed from seeds that orbited the earth on a NASA shuttle mission. Perhaps zero gravity played a role in some of their unusual and striking characteristics. In addition to the green edges, they tend to be large growers and enthusiastic bloomers. 
Plants in this series have "Ever" in their names: ‘Optimara EverLove', ‘Optimara EverHarmony', 'Optimara EverGrace'. Sometimes stores sell plants with no-name Optimara tags, but if you see big, wavy leaves and a ruffled, green-edged bloom, you're probably looking at a "space baby." I'll take frilly green African violet blooms over little green men from Mars, any day.
Other green blooming violets have been given unusual and creative names, such as ‘April in Paris', 'Brussels Sprouts', 'Garden Party', 'Mint Julep', and 'Winnergreen'. ‘Emerald City' is a striking chimera with a green stripe down the center of each petal. ‘Delta Frog Prince' and ‘Wrangler's Green Pastures' are two popular standard varieties with green-edged blooms (see photos).
"Flowers are red... and green leaves are green. There's no need to see flowers any other way than the way they always have been seen." -- Harry Chapin lyric
We're used to green leaves and colorful blooms on our plants. Maybe that's why we're so captivated by the unexpectedness of pink variegated foliage or green blooms. Whether we accept them as a genetic quirk or attribute them to Leprechaun antics, green blooming plants are fun!
For more information, check out the FAQ and the extensive list of links in the "sticky" thread at the top of the African Violets and Gesneriads Forum (subscribers only). More information and photos are constantly being added to the African violet entries in PlantFiles. AVSA (the African Violet Society of America) is an unbeatable resource -- there's probably an African violet club near you!
 for more information on these plants, see Optimara.com
Photo Credits: Thanks to Begoniacrazii (Delta Frog Prince and Wrangeler's Green Pastures), Mgarr (Irish Flirt), and Wayne_Susan (Optimara EverGrace) for their wonderful PlantFiles photos.
Photos of Lil Bit ‘o Irish (with Kermit), Petite Blarney, and Optimara Little Crystal in a Belleek pot (thumbnail) were taken by me.