Q: What color is a spaceship?
Several answers and comments on Why were Europe's first few satellites so stylish? Why the pronounced alternating white and black stripes? contain phrases like "thermal control".
This is back before fancy materials could have both high thermal infrared emissivity and high visible light albedo at the same time. (see answers to Why are RTGs different colors?)
But I can't see why the alternating high/low and low/high ($\epsilon/a$)† stripes would be better than just slapping on a coat of gray paint. Did they simply not have gray "space paint" back then and so the stripes were a work-around? Or were there some thermal or other spaceflight or testing advantages that stripes had over a a solid gray?
† $\epsilon_{ir}/a_{vis}$ would be thermal infrared emissivity and visible light albedo pairs, not meant to be as a simple ratio though. For an equation using these search this site for "spherical cow temperature".
Shamelessly cropped from images in this question and answer(s):
On other satellites, such as Explorer 3, reflecting oxide stripes maintain the average inside temperature between reasonable limits; 30 and 100 degrees Fahrenheit.
A better archived version of the video can be found here