As evidenced by the answers here, and in other UX.SE questions, there are many ways to go about it. This gives us a hint that there are no standards, conventions, or guidelines to follow -- though it doesn't preclude those forming in the future.
The absence of such standards is not surprising: a list can have many representative forms -- bulleted, with or without images and thumbnails, descriptions, attributes, and so on -- and has to adapt its specific form to a variety of different environments and needs.
Thus, the best we can do is turn to research on generic ways to differentiate items in a list. In 2016, Nielson Norman Group measured that:
Users are roughly 37% faster at finding items within a list on a web page when visual indicators vary both in color and icon compared to text alone. If choosing between using color or an icon, icons with strong information scent perform better than color alone.
From this research, we can take away that if the attribute of "newness" is the most important differentiator in your list, then use variations in color and icon to highlight the difference. Color alone helps, but does not perform as well as both.
You can see that the examples in other answers use this technique, suggesting that common implementations follow the research.
When faced with this problem, my recommendation would be to evaluate your list's specific form and introduce variation in color and icon to highlight the most important attribute. If there are many important attributes, provide a way to sort and filter.
NEW ITEMtag mentioned in one of the answers.