Possible Clues:

• During match, muddy ground becomes yellow
• Pigment from marshy ground buried in quarry
• No end of frolic, say, got up in yellow
• A mob jostling, in reaction egg's thrown over -- yellow
• Maybe bridge crosses land that's wet and yellow
• A gum resin from various Asian trees, used as a yellow pigment
• Yellow, but willing to cross marshy ground
• Is this pig meant, by the sound of it, to be yellow?