Incorrect calling conventions for *-color()

[nex3]

The adjust-color(), scale-color(), and change-color() functions should all allow exactly one positional argument and any number of keyword arguments. LibSass throws errors when zero keyword arguments are passed (as in adjust-color(red), which should return red) and fails to throw errors when more arguments are passed by position (as in adjust-color(red, 1)).

[nex3]

The error messages when a non-number is passed to any keyword argument (as in adjust-color(red, $red: a) are also wrong. LibSass says not enough arguments for `adjust-color', but the issue is that one of the arguments has the wrong type.