OptiSystem simulates systems, so in this view you are setting the parameters of components and simulating the resulting system. If you want to design a component and extract these details then you are looking at OptiFDTD (which can handle reflections).
In OptiSystem we do not have an exact component for creating different reflections at different wavelegnths, although we do have a Thin Lens component for simulating a single wavelength signal. You could use the Matlab component to set these values.
Regards