Proper exposure. That really is the only way, and since supplemental lighting probably wasn't an option here, you're pretty much threaded. There are times when you just can't get the shot you want....I've somehow got the colors out-of-gamut, how can I tell and how can I stay away from doing that in the future?
Well, the tones look flat and the colours appear muted because of the lack of shadow and highlight. Even with a good tan, the orange people in number three caught my eye and then I looked a little closer and noticed there are no real blacks especially in the huge shadow of the wheel well where you would expect to see it. So if you keep looking, the reds, white and blue in the half moon decoration all have two tones... a lighter and darker version of the hue. This is what tells me the tones have been clipped and have lost the subtle variations....so you see that I've somehow got the colors out-of-gamut, how can I tell and how can I stay away from doing that in the future?