This one is a simple trick — so much that I'm like duuuuh 🙈 again.
Gary Arndt, an award-winning travel photographer, made an ingenious point during the NY Travel Fest for amateur shooters: sometimes the best way of fixing a photo in shitty light is by turning the whole shebang into a black-and-white photo.
Travel photography, more than other kinds of photography, has its own unique set of problems. It's more or less an unpredictable situation everyone is dealing with: what the place will be like, how the weather will be and whether the lighting situation is going to be nice for the camera. The skies may not always perfectly align for the perfect shot and there's only one chance to capture it. As much as I'd love to control the San Francisco fog, dispense rain or play God, there's not much I can do. And sometimes the light really, really sucks balls.
So instead of taking a photo with flash—cause I'd hate you—the best cheat is to take a photo and turn it into a black and white photo to get rid of any unfavorable lighting or colors. Some photos are going to turn out better than others, due to different levels of contrast, but it's still a pretty brainless way to fix the problem.
Speaking of, JP Danko at DIY Photography has an amazing tutorial on how to do this with fantastic results. Beats chunking the photo, yah?