So, assuming this is right, why can two people with red hair get brown haired children? I thought red is a recessive trait, meaning you can only have red hair if you get it from both parents and therefore you can only pass red hair on.

Possible basically butchers recessive genes(and dominant too if you want to nitpick likely vs possible). Anything is possible if both parents carry a recessive gene. You might as well put blue hair in there because “it’s possible if someone in the family had it before”. It’s a very simplistic explanation of inheritance. It should at least include the grandparent generation to demonstrate how and where recessive genes work. This isn’t really a “guide” - barely an infographic.