How do you make potions?

[Gork]

i got all the ingredients and a table of alchemy, yet i can't figure it out the right combination of the mixture.

[Rithm Fluffderg]

You're given a color in one of the corners, you have to try to mix the ingredients together in a way that closely matches that color (the closer you are, the better the results, I think...)

The water serves to dilute the mixture, and can return it back to the starting point. Sometimes it's necessary to get to the color.

[Tedesche]

The mixtures are different for each heroine you create, and you have to do them each time you brew a batch of potions. Personally, I find this rather annoying, but it's how the game was done. I recommend saving before you brew a batch and using systematic trial and error to figure out the correct mixture for your heroine, then recording the ratios in your in-game note file (obtainable from the starting chest in the Adventurer's Guild in Fortigsuna, if you haven't checked there already).