Dark and Light - Their heads bent together, one jerking about. Sherlock's dark curls bobbed as he pointed out the facets of invisible knowledge that sparkled on the edges of the room. The other was still, mostly, John's blond strands catching the light as he turned slowly, taking in another side of the information, reflecting the information into questions. The hum of voices was cut with a clap, midnight hair spinning as Sherlock exclaimed in delight, and he dashed away from the house, away from the streetlamps. John only took a moment to start after him, sun bright hair and jumper the last thing to fade from view as he followed doggedly.
Intelligence and Ignorance - Typical and Atypical - John sometimes thinks he's the smart one. His knowledge of social intricacies managing to smooth their way through a case. Although if that were true, how would Sherlock have solved any before him? Sherlock knows the words, the motions, the emotions one shows and fakes and uses in "normal" interaction. It's just not efficient enough to merit use, and it's never felt right anyways. It's a rarely needed evil. Until those times, Sherlock doesn't mind John trying to fill the supposed gaps. As long as he's there, Sherlock doesn't mind.
Clothed and Unclothed - Rich and Poor - Sherlock likes clothes. He buys the best and wears it well. John...got over the first in the Army, not that he'd ever had the chance to develop an appreciation in the first place, really. He doesn't miss what he's never had. John also doesn't mean to influence Sherlock that way, he'd swear if anyone asked (no one has), but sheets do tend to be comfortable. They're comforting after a bad sleep, more so than a tatty robe. Not as easy to wear, so he stays inside his room when he does. Why and how Sherlock picked up on it is something he doesn't want to know, but seeing Sherlock wander about in just a sheet does make him smile.