(If they are petstore bettas, it isn't advised to breed them, they'll probably be too old to breed anyways.) Because you don't have any idea at all their genes, you'll have a mish mash of colors. Betta's are known to get coloring from grandparents are well. Because you didn't say what tail type your male is, I can't tell you the finnage. If he's a veil tail, you'll have combtail fry. Combtails look a lot like veiltails that tailbite.
WELL I BOUGHT BOTH OF MY MALE AND FEMALE BETTA AT THE PET STORE AND THEY STILL END UP Matting after 3 day the female look like she 11 month and the male i cant bearly tell but he was ready nd my male is a VEIL TAIL BETTA ,,,YES I UNDERSTAND THAT THANXS ALOT
I'm unsure as well so far, but perhaps you can post a picture of the two you wish to spawn? This would give a better idea for others to approximate on. As stated before though, it will be difficult to get a ball-park figure on the colors and tails due to being pet-store.
@KOKONOKO I HAVE MY ORANGE VEIL MALE ON DISPLAY. AND MY FEmALE IS IN MY ALBUM SHE THE LADY WITH THE BIG Belly...well my orange male matted with the female august 7, an the baby was born on the 8 I Noe it was weird the was born the next (2days old frys now) my bettas are in my album don't get confused I have a dark blue and black female veil tail u might tell the difference...