Suillus question

[BROCSMAN]

I gathered a couple of fruit bodies today, which I immediately thought were S. luteus. It was growing with pine, so I'm fairly confident of the ID. I just had a quick look in Michael Jordan's book however, and it offers no chemical tests, but suggests that S. tridentinus, which grows with Larch, turns vinaceous with Ammonia, so I tried a drop of Ammonia on these, and they immediately went pink.

Can someone tell me if this is well known as a test for this species? Michael Jordan doesn't seem to know about it. I haven't got a good boletus key at present to check.

Thanks.

[BROCSMAN]

Now it's gone blue! Previously unchanging.