I can’t tell you how many times over the years I’ve implemented a custom ‘button’ like CSS implementation. Over the years I’ve used images, backgrounds, gradients, and opacity to effectively ‘highlight’ a control. All that works of course, but the problem with most of these approaches is that one way or the other you’re hard coding a color value, image, or gradient.
You certainly have a lot more control if you specify exact colors, but if you can pull off brightening, darkening, or even a hue-shift in a way that feels cohesive on your site, it’s certainly a lot less code to maintain,
.button.specific-button {
background: #4CAF50;
}
.button.specific-button:focus,
.button.specific-button:hover {
background: #A5D6A7;
}
/* vs. */
.button:focus,
.button:hover {
filter: brightness(120%);
}
/* or maybe you're super hardcore and do it everywhere */
:focus,
:hover {
filter: brightness(120%) saturate(120%);
}