I have noticed over the years that it is qutie common to have sap with a yellowish tinge. I've also noticed that sap that is a day old or more, will get a tinge of yellow to it sometimes. Some would say that your drilling into dark colored or decayed wood. I never stick a tap into that kind of wood when I hit it, so am not sure why the yellowing. Sap isn't clear water, so that would expalin some of it. The syrup has never been afected to my knowledge.
Mark
Where we made syrup long before the trendies made it popular, now its just another commodity.
John Deere 4000, 830, and 420 crawler
1400 taps, 600 gph CDL RO, 4x12 wood-fired Leader, forced air and preheater. 400 gallon Sap-O-Matic vacuum gathering tank, PTO powered. 2500 gallon X truck tank, 17 bulk tanks.
No cage tanks allowed on this farm!