You probably could not tell if a type 5 liked you or not.
Largely, we deal with people and day-to-day things in an objective way. This means not allowing our personal feelings reflect upon how we treat someone.
Direct assaults into our interior are the only way to find out.
Two methods come to mind.
1) "Please, honestly tell me what you really think about me." Say it in a serious way, so they know you're being serious and want a serious answer. If the 5 likes you or is neutral, they'll give you a positive review. If something bugs the 5 about you, but they still think you're okay on the balance... they might point out the thing about you that bugs them. "You're so chaotic." "It's difficult because you're bossy." Getting a slightly negative review from a 5 is actually not a bad thing if you want to improve your relationship with them. It lets you know what to work on... and once the 5 has aired that grievance, they're likely to cut you some slack in that department since they got to speak it aloud (a rarity for us.)
Then there's the chance we utterly loath you and have to lie about what we think. We'll just try to give non-committal and totally un-detailed answers. "You're okay. Yeah, I like you." So you'll get a neutral review if we really do not like you... though, you'll also get a neutral review if we're neutral toward you. This is where it's hard to tell.
2) Attack method #2 is to try to close distance with the 5, relationship-wise. Invite them to do something only a friend would... or tell a joke that only a friend would tell... do they smile? Or do they just shrug and plaster on a fake smile, waiting for the next opportunity to get away from you?
A 5 will definitely not have a problem spending time around someone they like. I'm not talking about conversation, but being in-proximity to that person and perhaps doing activities together. Fives will try to distance their proximity to people they dislike. So any cues you might get, are going to be literally a matter of how many feet are they away, and for how long are they willing to stay there. Around people they dislike, they'll find more important things to do, than give that person any attention... but they'll give that person attention if they ask for it.
Also... even if a 5 doesn't like someone, that's usually pushed back into the rear of their mind. It's not that important, unless the issue of friendship/relationship comes up.
And I totally agree with the above posts. It's difficult for a 5 to not like someone. That person has to have done something to the 5 that really irked them. By default we either like people or are neutral until we've finished gathering our impressions.