You don't need to have a formal UX education to have good instincts about what good UX is. You just need to stick to your guns and fight for what you believe. Not everyone is going to agree with you all the time, no matter how good you are, but you have to present your case in a logical, data-driven way. You have to be confident in your knowledge, if you're not, read some more books until you become confident.
You can't say "That button shouldn't be yellow because yellow is ugly." You have to say "I don't think that making the button yellow is a great solution because it might have the opposite effect. Sometimes a difference in color can make a button stand out more, but if it looks too different people can miss it altogether. But I'm assuming you don't think it stands out enough, so let me give it another go and see if we can solve that."
Sometimes people who aren't schooled in design or UX ask for something specific like "I want to make it flash" but what they are really asking for (and what you have to learn to decipher) is to make that stand out more. They know that it's not standing out enough, but they don't know how to express that or explain what they think is wrong, so they come back with a consistently horrible solution. You just have to figure out what they're trying to accomplish.
I'm pretty good at handling these types of situations, it's kind of my thing. It just takes patience (you have to dig for answers), and focus.
All that being said, sometimes its not going to fly and you're going to do have to do what he says. It's happened to all of us at some point, you can either deal with it or find another place to work. I had this problem at my last job, so I left and found a place where they love my input and have a strong desire for good UX and I've never been happier.