There are many dyes available for hydraulic oil .I have used Toro for years .
This tiny bottle will turn 20 liters of oil red .
Here is what it looks like in my measuring container . A lot of people like the dye and think it's for seeing it on the turf quicker if a leak happens . My experience is most operators tend to not notice and keep going . We have had a few incidents recently but the mature operators were aware and shut down their machines as soon as they noticed. Our fleet is getting older now and is time to remind the operators of the protocol in the event of a leak . The number one reason we use the dye is to be able to see a leak during regular maintenance trying avoiding the dreaded leak on the course . Many times leaks where caught before they become an issue . Sometimes it just involves snugging up a hydraulic line fitting .