This is FANtastic. Apparently back on October 12, 1951 when they were filming the sixth episode of I Love Lucy, somebody in the audience snuck in with a 16mm color camera and filmed the filming, grabbing snippets here and there. So you get to see the actual colors of sets, costumes, Lucy’s hair–the whole nine. They’ve taken this and thrown in some bits from the actual episode so you can get some context–this is available on the most excellent Complete Series DVD.
You can read the full story over at TV Series Finale, regarding this and the split-screen bit of the colorized version of “Lucy Goes to Scotland” I’ve got for you after the break. Found all this via Mark Evanier.