If a bike is new, or paint is in overall good shape, or recently touch up/sprayed and gets chipped, and you don't want to 'go heavy', paint pens work well.
I've done a ton of touch ups on black frames or silver paint chips, or chrome.
They also come in most standard colors and some metallics, but it's tough to match. Black comes in gloss or flat.
Get the chip real clean with solvent of course, and try to avoid leaving too much paint in the chip...it will run or sag.
Paint will usually "flow" into cracks.
I showed classic & vintage Brit & Euro bikes for years that I also rode (never owned a "show-only" bike!) and part of the show prep was fixing paint chips, nicks & cracks.
I know were not "trophy hunting" with our li'l T-Dubs, but who doesn't like to have a good looking, corrosion free bike?
Ditto all above with small bottles of enamel & small "artist" brush.
This is usually better overall, for sure on larger chips.