Color polarization (obv made up term) is what I found when messing around with phot and filt. Black phot (Ctype 0) dissapears a few frames after spawning. Don't understand why but it happens, a NOT filter applied onto white phot (natural phot, the one you place down) will turn from 1111111111111111111111111111111 (2147483647, phot and filt's colors are in binary I believe) which is white to 000... (31 0's in total) ..000 Which (unsurprisingly is 0) is black. Black phot again, though, dissapears, so this would make white phot in a not gate vanish, but if the phot is even just SLIGHTLY colored there will be an impurity. say 0000000... 00001 (1, which is blue phot). Wil transform to 1111111.... 11110 (2147483646, which is light yellow phot), and as such will then pass through, into the re-whiter, and pass out of the filter as white.
Black phot does dissapear frames later. Which seems to be useful for particles that dissapear shortly. Maybe as a heat conductor (phot and the energy particles conduct heat) that turns off and on with just a filt setting or something.
Stuff with a ctype of zero disappearing is a well-understood phenomenon and it's used a lot in FILT electronics. mark2222 has a tutorial on it, among a lot of other interesting things.