As usual, it is the style masters of yore that set the standards. If you are to wear a khaki suit, you have to decide how it will look.
The “problem” with khaki suits are not the suits, it is because many times the people who wear them do not decide whether they want a more casual look or not. This gentleman does not have this problem.
Look at the patch pockets, the way the top button of his three button jacket is rolled over (I do this too), plus the panama hat is just perfect for summer. If you’re going to wear a khaki suit more formally, make sure it doesn’t have patch pockets, that it is not rumpled at all, and pair it with darker accessories: black or dark brown shoes/belt combinations work better than the cognac brown that he’s wearing.
That’s because he wants to, again, be more casual. So decide what kind of khaki suit you want, what you want out of it, and proceed from there.