My PS tried to aspirate, but when he pressed on my tummy, dark red blood came out of the needle hole. Is this a seroma? (Photo)

If after the drainage procedure you reaccelerated the fluid within three hours, then a more definitive procedure may be required than in-office aspiration.  Dark blood indicates that this is an old hematoma.  If clear straw colored fluid is removed this is a seroma.

Dark red drainage is probably a hematoma that is starting to break up. It is important that it is drained so as to prevent prolong convalescence and more scarring.

From your description and photos, it appears that the dark red blood is from a liquified hematoma.  Sometimes when these form after surgery they clog up the drains and don't come out.  At this stage, the hematoma has started to liquify and should be easy to drain by serial aspiration or by placement of a small drain.  Your outcome should be good.  Discuss it with your surgeon as to which way to proceed.