Immediately after teeth whitening, will regular butter stain teeth?

Butter should not cause any staining of your teeth. You should avoid foods/drinks with artificial coloring in them such as sodas, curry, red wine, etc...Usually it takes 24 to 48 hours for teeth to get rehydrated and become somewhat resistant to picking up stain. 

Butter is fine  but stay away from food colored beverages or foodstuff such as grape juice, staining fruits and red wine or anything that would stain your tongue the color of what you ingested.