To stare at something is to gaze at it fixedly and intently, with eyes wide open as from surprise, wonder, alarm, or impertinence. To gawk at something is to stare at it openly and dumbly, and a little intrusively. Gawking has negative connotations and implies a lack of politeness when noticing or observing another person. You’ll find it used often of tourists gawking at attractions or at celebrities, or of nosy onlookers who, in their oblivious behavior, are perhaps causing a scene themselves. Gawk is similar to the verb gape, “to stare with the mouth open, as in wonder,” though gape is less used of people and more of sights and scenery that stirs amazement or disbelief.
Colorful literally means full of color, especially a lot of different bright colors. It can also be used in a figurative way to mean rich with interesting or vividly depicted elements, such as characters or events. Used as a synonym for the literal sense, vibrant means vivid, that is, strikingly bright or intense in color. Vibrant is related to the verb vibrate, a connection that makes more sense with some other meanings: vibrant can also describe things that are pulsating with vigor and energy (one might say vibrating), such as a vibrant city, and even personalities that are energetic and full of vitality. Use of the word vibrant to describe something that is brilliantly colorful suggests that the intensity and array of hues has an energizing or stimulating effect.
The adjective useful is commonly used to describe things that are in some way helpful or advantageous for a particular purpose: The recruiter provided the job seeker with a ton of useful information about the role. The synonym handy is a bit more informal and is used especially to talk about things that are convenient or that make things easier: The article was published alongside a handy glossary of terms so readers wouldn’t get lost in the technical terminology. Handy appears quite frequently in the phrase “come in handy,” as in, The article listed a bunch of tips and tricks that might one day come in handy.