I grew up with a black and white television set, so I was completely oblivious to that famous switch in The Wizard of Oz between sepia Kansas and the Technicolor dream world.
The yellow brick road, the ruby slippers, and Emerald City are so richly saturated with color on screen that it’s hard to imagine the film without it!
Well, not really. I saw it every single Easter on network television, in black and white. When I saw it on the big screen in college, it blew me away. Likewise, Gene Kelly's The Three Musketeers was like insane, with Vincent Price as Cardinal Richelieu (in red) and Lana Turner as Madame de Winter (in green), and Gene Kelly in brown, doing all his own stunts.
I'm now experiencing some of the same thing as I re-watch original Star Trek on Netflix. I had never seen the episode "What Are Little Girls Made Of?", only stills of the great Ted Cassidy playing the android Ruk in the book Monsters of Star Trek when I was little. So many of the monsters in that era were slooooow, like the Gorn, but Cassidy's Ruk was both quick and stealthy, as well as inhumanly strong. There were no wires helping him lift Kirk into the air, kicking like a child, and hurl him across the room.
I had no idea that the corridors were not cold gray stone, but lit in a pastel nightmare of pink and purple and blue. This is happening over and over as I watch the series.
In "The Galileo Seven," the fuel dump from the shuttle looks SOOOOOOOO much cooler than I was expecting from 1968 model technology. Though as it turns out, this particular effect is CGI, added for the Blu-Ray (still cool). I guess Netflix is not a purist. Neither am I, though I do think Lucas over-did the revisions in his remasters.
Every planet the Enterprise orbits has an atmospheric halo that was totally invisible to me as a youngster, often of a surprising color. The purple skies of Starbase 11 were another delightful surprise.