Answer: Well yes you can eat it. It isn’t poisonous. But do you want to eat it? Probably not. When broccoli turns yellow or flowers it becomes very bitter. The bitter taste gets even worse when you cook it. So if you really don’t want to waste it, you could eat it raw. If there is only a little bit of yellow, you might be able to cut the yellow parts off and use the rest. Let your tongue make the final decision. If it tastes too bitter than do not eat it or add it to something sweet that will counteract the bitterness
If we are talking about baby broccoli or broccolini, it often has a bit of yellow on the buds. It usually doesn’t taste bitter.
To learn about growing your own broccoli, check out my experience with growing the packman variety this season.