If Dean Winchester was the deep, introspective, philosophical type of person, he'd look at Castiel - all mighty Angel of the Lord - and he'd describe the dark haired Angel as...well...beautiful, breathtakingly beautiful. He'd notice the Angels pale, almost porcelain like skin. He'd notice the intense, other worldy blue of Cas' eyes, and how just staring into those impossibly blue eyes makes Dean feel a calmness, and peace that he's never experienced in all his days. He'd notice the way the Angel tilts his head to the side, when he doesn't quite comprehend something. Dean would hear Castiel's voice, and instead of hearing his usual coarse, rasp - he'd hear the hidden passion laced into all of the words Castiel has ever spoken to him. He'd notice the Angel's long, elegant fingers, he'd wonder how it would feel to entwine their fingers together. He'd notice Cas' long, swanlike neck, and he'd long to press his lips to the hollow in his throat. Dean would notice how Castiel smells of ozone, of raw power, yet with under currents of fresh summer days, and newly fallen snow...all mixed together, into something so completely...just Castiel.
But Dean Winchester is not a deep, introspective, philosophical type of person. So he'll continue driving his beloved Impala, drumming on the steering wheel in time to the Metallica cassette that is currently playing, while the object of all his desires, sits silently in the back seat of his car.