Act 2, scene 1 of The Merchant of Venice opens with Portia and the Prince of Morocco already in conversation. It appears that the Prince has been doing most of the talking, but Portia doesn't seem to mind. He's a gregarious, straightforward kind of man: honest and friendly in his own condescending princely way.
As Portia and the Prince enter the scene, the Prince is talking at considerable length about the color of his skin.
When the Prince stops talking, Portia responds, ignoring his comments about his skin color. Portia says, basically, that whether she likes the color of his skin is pretty much irrelevant because whether or not she likes him is pretty much irrelevant: her father's wishes are that the casket test will decide her marriage partner.
Portia tries to let him down easy by adding that he's the best looking guy she's seen so far for the casket test:
PORTIA: Yourself, renowned prince, then stood as fair
As any comer I have look'd on yet,
For my affection. (2.1.20–22)
Of course, he's the only guy she's seen so far for the casket test. She could also be saying that he has just about as "fair" a chance at winning her as anybody else, knowing full well that his chances are somewhere between slim and none, no matter what he looks like.
The Prince nevertheless continues to plead his case, seemingly ignoring the rules of the casket test, as if Portia could choose her own marriage partner:
MOROCCO: By this scimitar,—
That slew the Sophy, and a Persian prince,
That won three fields of Sultan Solyman,—
I would o'erstare the sternest eyes that look,
Outbrave the heart most daring on the earth,
Pluck the young sucking cubs from the she-bear,
Yea, mock the lion when he roars for prey,
To win thee, lady. (2.1.25–32)
The Prince seriously overstates his case, but Portia appears to pay no attention to his boasting. He's a warrior prince. It's just the way he talks. She also ignores his melodramatic plea for sympathy if he loses:
MOROCCO: And so may I, blind fortune leading me,
Miss that which one unworthier may attain,
And die with grieving. (2.1.37–39)
However, we know that he has all of those virgins waiting for him back in Morocco that he mentioned at the top of the scene (and so is unlikely to die from grief):
MOROCCO: by my love, I swear,
The best-regarded virgins of our clime
Have lov'd it too (2.1.9–11)
Little does the Prince know that he's never going to replace Bassanio in Portia's mind or her heart.
"You must take your chance," Portia says, getting right back to business. She explains the rules of the casket test, the Prince agrees to abide by the rules, and they agree to do the casket test after dinner. One of the rules is that if the Prince loses the test he's not to speak to Portia again, ever—which might be something with which Portia can agree wholeheartedly.
In all, Portia seems very business-like towards the Prince: cordial, but non-committal. If she has any good or bad feelings towards him, she doesn't let them show and says nothing that would lead us to believe she has feelings about him either way.
As far as Portia's lines about the Prince at the end of Scene 7 are concerned:
PORTIA: A gentle riddance:—Draw the curtains, go;—
Let all of his complexion choose me so. (2.7.79–80)
Portia has given no indication in her scenes with the Prince, or anywhere else in the play for that matter, that she holds any prejudice whatsoever against dark-skinned people. "A gentle riddance" would seem to support that interpretation.
"Complexion," then, would refer to those of her suitors with similar personality or character traits, not to those with the same skin color. Portia hopes, and intends, that everybody but Bassanio will fail the test, and she'd be happy to be rid of all of them, whoever they are.