The way I understand us seeing colors: for non transparent objects, light of specific wavelength (that matches the color) bounces off object (the rest is absorbed by object) and hits cones in our eye, then based on combination of cones activated (RGB) we perceive color.
For transparent things light does not get absorbed but goes through the object (nothing gets reflected, nothing hits retina) and we see through it.
For colored transparent objects all but that specific wavelength goes through, specific color gets reflected, all others go through.
Now obviously I must be making a mistake somewhere in the above…
Why when light goes through colored glass shadow becomes colored to the color of the glass? (Shouldn't it be 'White Light' minus color of the glass? e.g anything but that color)
Best Answer
Let's consider that transparent colored glass, which color wavelength is $\lambda$, It is colored because all the other wavelengths are absorbed and that specific wavelength $\lambda$ gets reflected, In the case when light goes through it, same thing can be observed, all the other wavelengths are absorbed and only that specific $\lambda$ gets through.
For illustration consider the image bellow:
The first filter looks red($\lambda = 700nm$) because all other wavelengths are absorbed and only red is able to go through it or get reflected, Same can be observed with the rest of the filters.