Remembering or seeing thought in colors is just a tool of memory. All any memory is is a neural sequence similar to that of a real experience, but with a tag on it so your body doesnt confuse it with reality. When the tag malfunctions, thats when you get shit like hallucinations, dellusions, and conditions such as schizophrenia.

Light at the end of the tunnel is a very common NDE, and even a very common response to some drugs. It's caused by neural noise.

If you started with very little neural noise and it gradually increased, the effect would be of a light at the centre getting larger and larger and hence closer and closer....the tunnel would appear to move as the noise levels increased and the central light got larger and larger....If the whole cortex became so noisy that all the cells were firing fast, the whole area would appear light (Blackmore 1993, 85).

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