Telling Metric From Inch-Series Fasteners

A company called Metric Blue offers metric bolts tinted blue.  Why blue? So that when you have mixed metric and inch-series parts and fasteners it is easier to determine which standard you are working with. Company literature says, “By differentiating the metric fasteners (and tools) through our “blue” coating,  we’ve eliminated the risk of failure or accidents due to mismatched components.”