Did you use water in the extraction?
You will want to go back and do a liquid-liquid extraction to clear out impurities.
I suspect that you may have accidentally gotten an insoluble salt from fertilizer residue in the buds, possibly reacting with salt in the butter itself- normally this is not a problem at all, since most of us do butter in a melted butter/water/plant matter combination, and the ionic substances actually go into solution in the aqueous phase and are washed away.

Seriously, read the washed cannabutter thread. You can still perform a wash on your butter at this stage, no problem at all!
stinkyattic Reviewed by stinkyattic on . orange salty like residue when making butter? I am not sure what happened, but this is only my second time making cannabutter...There was a rust color residue that settled at the bottom of the butter after I finished..The smell was very potent, and it had some granular salts in it? The color scares me though..I know the buds had a lot of orange hair in it and some orange, and also it was super sticky and strong smelling..I have the mixture in the fridge right now. I just wanted to get some input as to why it may have turned orange? Rating: 5