Defining a dark color in the media/arch.css is needed to make it readable
for those whose default GTK foreground is a light color.

Otherwise, reading the search entry and comboboxes is nearly impossible.
The bugs website has #03008f, so maybe that's a good choice.

Example:
.greybox input, button, textarea, select {
color: #03008f;
background: #e1e3e6;
border: 1px solid #8faecd;
}