Tiger's talk with Neptune is after he frees the slaves.
http://mangastream.com/read/one_piece/58373218/15
Tiger returns and heads to Ryuuguu Palace. On the next page, they hear the news that Tiger freed the slaves (no timeskipping between these two pages).
Tiger is talking about what he witnessed and that he freed the slaves when he was at Mariejois. He didn't climb the Red Line.
The image of him in the Hawaiian shirt is jumping back a while, describing the conditions under which Tiger left, and what happened to the his companions after he left. Those panels showing Jinbe, Arlong and Macro are events taking place before the rest of the events on that page (i.e. the "he freed the slaves" comment)
When he's talking to Neptune, he has the same outfit. Same shirt, same pants, same dark sandals, same pack he was carrying when he spoke with Arlong and Jinbe.
I do wonder, though, how the Hancock sisters bought in to the fact that Fisher Tiger actually invaded Marijois instead of breaking out of it? They would have been slaves there at the same time, and even if the sisters didn't know about Tiger's presence as a slave in the city, one would assume that they would be told what was happening during the attack itself (i.e. "A slave is going wild and freeing all the others!" vs. "Somebody invaded the city to free all the slaves!") but maybe there's something to explain it, or it's inconsequential.