SocketsSticks that are RED indicate Standard/SAE sizes measured in inches. The labels in these packages correspond to those standard sizes, allowing you to organizes your sockets, accordingly.

IMPORTANT: There are two sizes of SocketSticks for the 3/8" socket drive. This is because of the wide range of socket sizes available for this drive. Please pay close attention to the socket sizes supported by the small base and large base SocketSticks for the 3/8" drive, described in RED in the product details.

Also, V-Blocks come in RED. This is important if you're organizing Standard/SAE size wrenches (i.e. open-end or box). Its not as important for socket drives, screw drivers and other tools that don't have measured sizes. For those tools, you can just pick your favorite color - RED or BLUE.