I read a lot about preserved lemons (TLDR: quarter them, and keep them in a mix of lemon juice and salted/brined water for 10-30 days), and I'm trying it with limes. But...  Two things concern me about my current mixture:   The lime skin, which was a nice vibrant green, is turning a dark greenish (almost brown) colour In some places, the colour leeched off entirely and it's white (like the inside of the rind   Am I doing this right, or is this starting to rot?  I brined them in a combination of salt, water, and lemon juice for about three or four days prior to noticing this. Now (another four days later), they're even more dull-coloured.  (I don't have a picture, sorry. On closer inspection, the dark green/brown looks like it's fading.) 
I have always found that squid needs to be only cooked for 1 minute (2-3 minutes if battered and deep fried). Any more or any less results in very rubbery texture.  It can also be slow cooked for an hour or more in a soup so that it becomes tender. 