As explained to me by someone with more experience in these nuances than I have, light refers to color saturation or intensity. Pale is a matter of how much white is mixed in with the color. The more white, the paler the color.
This distinction is important in French even if we are more casual about such terms in English.
Colors are a bit tricky in French. When you have a modified color, it becomes invariable. This means that you don't alter it to account for gender or number.
Les livres sont vert foncé. (dark green)
Nos clés sont gris clair. (light gray)
Mes fraises sont rouge foncé. (dark red)
Basically when you have two words in a row describing the color, the words stay singular and masculine.
Here's a good site that addresses this issue: https://www.thoughtco.com/invariable-french-adjectives-1368796
Agreed. The only place I've heard "pale" in the context of color is on BBC, so maybe Brits make the distinction? But colloquially in the United States, one would say "light yellow" in this context. That isn't to say "pale" would be wrong in the U.S. nor to say it's never used, but "light" is more common.