Cologne is much bigger than Frankfurt, and the gay scene in Cologne is the second largest in Germany (after Berlin). Check the Gay City Map (overview) on www.patroc.com/cologne/, the IC Cologne is near the venue with No. 18 on that map - so most venues are within walking distance or 2 stops with the underground/tram.

Because Cologne was widely destroyed by bombs in the last war it isn't very rich of touristic sights, besides of the cathedral which is really worth to see. But Cologne is a pretty good place for "to kinda blend in, hang at a coffee shop, eat a nice meal or two, go out to a gay bar and/or sauna". People there are usually nicer and more easy-going than in other big cities in Germany.

The 1-hour ICE train from Frankfurt to Cologne is 60 EUR (one-way), the 2-hour ICEs and ICs are about 45 EUR (one way). The 2-hour trains go along the Rhine river, with some spectacular views especially the first 30 min after Koblenz (coming from Frankfurt try to have a seat on the window on the right side).

Bon voyage!