I am asuming you want smallish ones for bouquets- not AA's so I'll go with some of my favorites that bloom non-stop all season & all with long enough stems to have nice cut flowers. However, you have to be aware that you have to disbud any dahlias a certain amount to get a nice cut-flower stem. You just pop off the 2 side buds of each central stem & you'll get a good sized stem on just about any dahlia.
White- Arctic Frost; Pink- Chimmacum Katie or Valley Porcupine- this one is so cute & lasts a full week+ as a cut flower; dark - almost black- Shadow Cat or Rip City; hot pink- Camano Electra or Pretty in Pink. (And of course- there's the old standby- Chilson's Pride that will put out a ton of blooms- it's pink with a white center - we don't grow it any more but it is a good cut flower.) I cut at least 40 blooms a day off of these plants & the color combo is GREAT- we have a couple of plants of each one at our son's place-- way away from the AA seed parents!

Suzanan: I use the Karma series for cutting. They are specially bred for cutting, long sturdy stems. I planted 50 mixed ones last year and I am still n the process of dividing them. The plants continuously produces all summer and fall. These were a HOT seller at our Farmers Market. Good luck. HEIDI