Using the urgency color plugin (bug #906516), one may want to mark specific tasks with dark background colors. For instance, overdue or urgent tasks may be marked with a darkish red background. In this case it is better to have a white foreground color - the text is more visible. This has never been a problem so far, since GTG uses a very pale background for tags-based coloring. For urgency-based coloring I think it makes sense to use dark backgrounds.
I propose a simple modification (see patch) to the lilblarch package, so that text is rendered white dynamically depending on the background brightness. The definition of the brightness is taken from here
http://stackoverflow.com/questions/596216/formula-to-determine-brightness-of-rgb-color
It is such that background colors determined using tags do not exceed the threshold, thus the original behavior (black foreground) is reproduced when the plugin is disabled. In a sense, even though the modification is applied globally, it is only active when using the plugin.
I've merged your patch: https:/
I also done a few changes: https:/
Closing as fix committed. Thanks for your contribution!