W3Schools.com, a website operated by the World Wide Web Consortium, has a list of 140 colors, their names and their HEX values. For these 140 colors, either the HEX value or color name may be used in HTML. Alternatively, HTML-Color-Codes.info has a wider range of HTML color codes.
The colors on W3Schools.com are considered Web safe, meaning that they are supported by all modern browsers. The website also includes references for checking similar shades and their HEX values.
HTML-Color-Codes.info includes a color picker that allows users to find the HEX value of any HTML color. However, not all of these are supported by all modern browsers, and they may not display consistently.