The Essex-based firm supplies more than 200 varieties to packet seed companies, mail-order outfits, professional growers, shops and web businesses.
Seedlynx said: "Some of the most exciting new sweet peas on the market now are a new category for which the term 'shifters' has been coined. The flowers open with one colour then, as they age and develop, a completely different colour emerges. This has resulted from cross-breeding between Lathyrus odoratus and Lathyrus belinensis".
The breeding work continues and more new varieties will be released in future.
Blue Shift, also marketed as 'Duchy of Cambridge', has flowers that are purple/mauve to begin with and then shift to a bright almost iridescent blue. Turquoise Lagoon starts out pink/lavender before changing to a turquoise blue.
"Unfortunately this changing colour is not easy to capture in still photos and we have not yet delved into the world of time-lapse photography," added Seedlynx.