In the past, CSS float properties were one of the main methods for arranging elements on a website. And if you’ve ever worked that way, you know that it’s not always ideal for complex layouts. Luckily in the modern era of web design, aligning elements has become much more streamlined thanks to Flexbox and CSS grids.
The hexadecimal colours and the rgba colours use amounts of Red Blue Green to describe colours. This is a nice analogue to how the pixels in the screen are lighting up but it makes picking a colour not very human friendly.
Part of the magic of these notifications is that they can appear even when we're not currently on that website to give us that information (after you've approved it). On mobile devices, where supported, you can even close the browser and still get them.