You might want to search for the type and model of the tach, that will likely take to a site and explain what the red light means. Most of the time the tach only ships with one light/ shift, you say you have two. The second one red is an add on and could be temp or oil warning, depends on how the builder configured it, you checked the oil? ojh mentioned it above and was a good suggestion for you to look into.

Happy hunting