Without know exactly what they are spraying, we cannot accuratly answer. If you can find our exactly what they are using, we can better assist you. Turf Mark Blue Spray Indicator Dye is not harmful on its own.
Yes, Turf Mark Blue Spray Indicator Dye is labeled to be used applied with herbicides and safe to do so as directed on the label.
Turf Mark Blue can be mixed with Bora-Care with Mold-Care at the rate of 0.02 – 0.04 fl oz per gallon, which would be a total of 0.12 – 0.24 oz in the 6 gallons the mix of Boracare with MoldCare (5:1 ratio) makes for wood treatment.