or css color audit, for those in the US
Based on article by A list apart - CSS Audits: Taking stock of your code.
While working on a site refactor I found these tools useful in auditing the CSS colour values being used throughout a large e-commerce site.
Run the node app against your css file(s) and get a list of colour similarity issues. Uses some complex maths to compare hex values.
Add as many colours as you need and compare side-by-side. Useful to see large colour swatches for comparison.
Paste your generated css into the input field to get a visual list of all the colours you're using plus hex codes. Handy to visually compare.