[Usability] Alternatives to hardcoded colors

[Jeff <web kiddo free fr>]

Hello, I'm a happy user of Pimlico Tasks (http://pimlico-project.org/tasks.html), and there seems to be a usability/accessibility flaw in this application: the tasks "priorities" are indicated by colors in certain cases. 

In the main task list, tasks with high priority are displayed in bold type text, "normal" priority is displayed in normal text. All that seems good so far, however the problem is this: the "low priority" tasks are displayed in hardcoded gray text. I find that to be bad accessibility, because it does not seem to bode well with most GTK themes. For example, with clearlooks, the text is readable (gray on white), but barely, and you need to have a powerfully-lit screen to contrast the text. Then, gray text is unusable in most dark themes too (gray on black).

I know that a lot of applications are in this situation. I would like your input as to what could be done to be able to indicate 3-4 levels of "priority" while still retaining an application that is not heavily theme-dependent for being legible (I'm also thinking of other applications such as Homebank, Specto, etc.), especially in GTK listviews or treeviews.

Thank you for your ideas.