it is....
if you kept 2 d.p.'s.... that's 6"... then you could have a couple corys/otos like they said...
If you kept 3 d.p.'s... (2 females to 1 male) that's 9". Then you could get only 1 or 2 cory/otos.
BUT!! Didn't he say he was looking for colorful mollies??
I have a 10 gallon and this is what I have in my tank...

3 balloon mollies (one black, one white, and one orange...they're beautiful)
1 male gourami (blue and red striped)
3 otos for my algae team
and some guppies!
I'd suggest everything but the guppies... they're breeding and overstocking me! I can't give them away fast enough.
If you did a tank with everything I said but the guppies I think it would be perfect... I filled my tank with red and black gravel and tons of plants! It's really quite colorful like you are looking for!! :-)