A variable declared as global in multiple functions (and optionally the base workspace) share a single copy of that variable. Any assignment you make to that variable in one function is available to all functions that declare it global.

If you intentionally use a variable in this manner, it is not a problem.

However, if you unintentionally use a variable in this manner, it can result in unexpected behavior. If the highlighting indicates that the scope of a variable spans multiple functions, and that was not your intent, remove the global declaration from the variable.

For more information on variables and the workspace, see Global Variables.