Riboflavin
“Micrococcus luteus (ATCC strain number 49442) develops a yellow color due to production of riboflavin while growing on pyridine but not when grown on other substrates, such as succinic acid.” - via Wikimedia Commons

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Riboflavin
“Micrococcus luteus (ATCC strain number 49442) develops a yellow color due to production of riboflavin while growing on pyridine but not when grown on other substrates, such as succinic acid.” - via Wikimedia Commons