In a web application I'm developing we categorize systems based on their criticality (1-4). A system might have connected emergencies, which have emergency levels (1-3). Combined they give you the priority of an emergency.
My first draft includes traffic-light colors for displaying emergency levels, but it's not really extendible as you only have three categories (green, yellow, red) and it's all but verbose.
For criticality I think about using basic shapes with increasing edge count: circle ●, triangle ▼, quad ■ (or triangle pointing up ▲), star ★ (from least critical to most critical).
The good thing here is that you can combine colors and shapes, but on the other side the colored icons still don't feel anything like easy to read.
Are there better design elements for showing such things? I'd rather not display these attributes as plain numbers.