system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do colourblindness correction sunglasses work?

I saw a video on Facebook today of sunglasses that allow colourblind people to see the full colour spectrum. I'm assuming that this is obviously doesn't work with black-white colourblindness, but how would it effect the most popular colourblindness disorders? I thought that this had to do with the inability to see certain colours, like red and green looking the same for example. I don't understand how looking through a specific substance could fix this?
gpt
If you take the most common case, which is red to green colour blindness, The persons red and green photopigments have more overlap than normal, making them unable to see certain colors. Colour blind glasses work in a way to alleviate this by creating a specialized lens that filters out specific colors. 

You can use these filters to target specific photopigments so you can affect  what wavelengths (or colours) the person can see depending on what colours they are struggling with.  Just because a person is colour blind doesn't mean that the colour they can't see  is completely invisible to them, they just need some fine tuning which means blocking out the overlapping wavelegnths to enhance the less common ones.