CSS color filters & black

I ran into an issue. Code like this:

.link:hover {
  filter: brightness(1.5);
}

… worked perfectly on a colored icon but had no effect on a text label. It turned out that the label used the color #000. brightness() is a purely mathematical function that multiplies the R, G, and B values by the given factor. This makes no difference for pure black, since 0 * anything = 0.