Making a line y=f(x) in the graph and setting the color there isn’t a lazy workaround - it’s the recommended way to format, since it gives you easy access to all of the things you can do with the function (dashed lines, colors, inequalities, etc.), instead of needing to learn a new mechanism.
If you need to specify a specific custom color, then we don’t have a well-supported way to do that right now. rawExpression and rawExpressionColor are deprecated and shouldn’t be used for new things.