Why is the water that drains from my new-to-me Norfolk pine yellow?

My son kindly dropped a 9 foot Norfolk pine. on me a couple of weeks ago. I love, love, love him (in spite of the fact that I’ve been downsizing my large plants by giving all but two of the them to MY SON!) and I have named him Ferngalee.

It’s been a bit of a rough go. First I repotted him. I kind of thought I shouldn’t but it hurt to see him in that tiny pot so I moved one size up, into a more decorative ceramic pot.

I had him on my north-facing covered front deck, and he just wasn’t getting enough light and the top was starting to droop.

Yesterday I moved him to the west side of the house.

I also threw down a temporary aluminum water catcher under him yesterday, and watered him thoroughly.

Today I noticed that the water standing in the pan is yellow. I’m pretty sure it’s not due to the pan, because I’ve had plants in aluminum pans (temporarily) in the past.

I read somewhere, long ago, something about what it means when the water is yellow, but all I can seem to find on the net is “yellow leaves.” Stupid internet.

I thought maybe there is a plant lover here who can tell me without having to research it all over.