@trinsec ahh yea if you can identify similar shades as different, but they seem very similar to you still then your not a tetrachromat.
A true achromatic would see two colors as distinctly different when to others they would appear the same or very similar.
You would be seeing colors other people cant see, but you wouldnt be aware of it and those new colors wouldnt have special names to you or would even be recognizable as colors others cant see.