Because there's a specific order that adjective types should go in: Quantity (number); Quality (e.g. bad, good, etc.); Size; Age; Shape; Color; Proper adjective (e.g. Italian); Purpose (e.g. "sport" in "sports car")
Deviation from this order happens sometimes, but usually for emphasis (e.g. big beautiful house). Normally a person would say a beautiful big house, but since the adjectives are flipped it puts more emphasis on both adjectives somehow.
In English, adjectives come before the noun. So pale comes before yellow which means the colour Yellow is pale. While, yellow pale means pale is yellow which of course does not mean anything. Similarly in French, adjective comes after the noun so "jaune pale" is the correct order