Phosphoric Acid Method Results

I am trying to isomerize CBD with phosphoric acid.

It usually turns a beautiful gold, but this time it turned brown.
Why is this?

Details.
The ratio of CBD : ethanol : phosphoric acid is 5g : 10g : 2g.
Ethanol was dehydrated in a 3A molecular sieve.
Phosphoric acid was baked in an oven at 120°C for 2 hours.
It was refluxed under atmosphere for 8 hours.
This time when I added the CBD to the ethanol it turned a little red.

Just lost my KOH and have not been able to do the Beam test.

What color was your acid comming out of the oven amber red or. Bordeaux red ?

Is this post distillation?

Phosphoric acid was clear.