My lo had no problems adjusting, but she's also only spit up a handful of times in her life (9 mo now).
Also use the purple one. Maybe you are feeding too much or he’s swallowing too fast. My baby spits up a little bit too but not every time, or at least not right away. Don’t be nervous. Its ok!
My lo still throws up after every feed. She’s going on 5 months next week