This is a globular cluster located in the outskirts of the Large Magellanic Cloud. The reason it looks so colorful is because it was imaged in red/near-infrared (the red channel filter overlaps both) and near-ultraviolet. HST is one of the only observatories still in operation capable of ultraviolet observations due to its location above Earth's atmosphere. Astronomers are especially keen to make use of its ultraviolet abilities before the harsh environment of space takes its inevitable toll on the telescope. Yes, the telescope will eventually stop working altogether, but even before that happens, the detectors which pick up ultraviolet light are also quickly losing sensitivity.
Globular clusters typically take on an overall muted yellow color in visible spectrum images, but the near-infrared and near-ultraviolet filters are very good at highlighting what might otherwise be subtle differences and the result is a beautifully colorful image. You might also notice the faint red apparitions of galaxies in the background. They are relatively faint in ultraviolet light, so they appear unusually red in this particular image, but their shapes are unmistakably galactic.
Data from the following proposals were used to create this image.
Red: WFC3/UVIS F814W
Green: WFC3/UVIS F336W
Blue: WFC3/UVIS F225W
North is 2.3° clockwise from up.