According to the
VIMS instrument, Titan's lakes are only millimeters thick which means the lakes are actually either dry mudflats or are coated with a thin film of something that block sunlight. No data from north polar lakes available yet, though. Specular reflections may have been seen.
Speaking of north polar lakes, Titan's thick atmosphere bends light which allows Cassini to peek lakes beyond the terminator that have so far been in darkness.
New dark splotches have appeared in the southern polar region suggesting that the lakes there are starting to fill as the southern summer is coming to an end. There apparently have been torrential rains in the recent months.