You can but the question is what does the filter block and so passes through to the sensor and therefore what the color changes are for the resultant image.
As a galaxy is considered "white" then the blocked wavelengths will not get to the final image. Generally they block the yellow and green area so the galaxy image would lose those and appear red+blue bias.
Looking at the box it blocks basically 530nm to 630nm also blocks below 450nm. So conversly passes 450 to 530, then 630 upwards. So images are blue and a bit of green, then red. You lose Orange, Yellow and say half the green. So a galaxy has no orange, yellow and reduced green at the final image.
A CLS filter does not block the City Lights, it just blocks the chunk of the spectrun where not city lights are, and it blocks any wavelength in that chunk immaterial of source.