The article itself is surface level and playful, not declaring the authenticity of the photo in question. Although some might see this article as an excuse to take a cheap shot at Trump, this photo did indeed go viral and it could be argued that it warrants a story. The author definitely adds some salt to the wound at the end of the article when she includes a couple of the most clever jabs at Trump regarding the photo, which I admittedly found funny.

The article says the photo was “adjusted” with (non-Photoshop) software so it's technically correct it wasn't photoshopped. But no journalism standard supports altering a photo's appearance to exaggerate ANY aspect of it, or to change the context by cropping. Without seeing the unadjusted photo, it's impossible to tell how ridiculous the fake tan looked to people who were there. Certainly, the Guardian would not have published the photo alongside its news coverage of the day, without confirming that the photo was legit. This story is a half-truth, unverifiable in the meaning most people will take from it.