Problem No. 74: Is green urea really green?

Green urea is urea based on green ammonia produced from renewable power via electrolysers and bio-based carbon dioxide and its colour is the same as normal urea. But in this round table discussion we discuss the possible causes for urea turning a green colour as found by the initiator of this discussion. We will learn that the colour of urea can be reddish or brownish in certain conditions where corrosion rates are high and/or oil fouling is high. But what can cause urea to turn green?

Ali Ançaza from Igsas in Turkey kicks off this round table discussion: Our synthesis section was blocked during a 12-hour shutdown. The synthesis section was then drained and emptied. While recycling the urea solution in the urea solution tank via the evaporation section, we noticed that the colour of the solution was green as you can see in the pictures below. I wonder what could be the reason for this? Has anyone experienced such an event?