While Maurice Noble's background painter Phil DeGuard is relatively well-known for his highly recognizable work in Jones classics like What's Opera Doc (1957), background painter Irv Wyner brought a similar, sometimes even more radical coloring style to Hawley Pratt's stylized layouts. They worked together in the Freleng unit from 1952 until 1957. Much later, Wyner worked for Jones on specials like Rikki-Tikki-Tavi (1975).
Here are four screenshots from Freleng's Goo Goo Goliath (1954) and eight possible sky colors only four of which are from this cartoon:
Which sky color matches which background?
(example: 1A, 2B, 3C, 4D)