Tin snips that are intended to cut straight through metal have insulated yellow handles. They are used when a straight cut is needed without any curve. Depending on your project, you may use many different designs of tin snips to create the perfect metal cutout.
Left-cutting tin snips have red insulated handles. These are used when cutting metal for things like duct work. The blades on left-cutting tin snips curve to the left. These cutting designs are necessary because heavy metal is difficult to cut when going around a curve. Because of its weight and stiffness, it doesn't give like other lighter materials.
With a blade that curves to the right, right cutting tin snips are intended to cut in a curve to the right and are color-coded green. It is helpful to have an idea what your finished design will look like before you begin to cut metal. This will assist you in choosing which tin snips to use for each section.
Compound-action snips are also called aviation snips because they were first designed for cutting aluminum to make aircraft. The design of these snips with compound action gives them a mechanical advantage over traditional tin snips. While designed for cutting heavier material, they work very well on tin and other lighter metals. They have the same color coding for left-, right-, straight-cutting design as tin snips. The blades are usually serrated which prevents slippage while cutting.