Hmm, I am almost scared to post already, but I will anyway since I am tired and it may help someone. Whoever figured out the initial color change sequence required, kudos. Patterns I noticed are as follows:
1) From left to right my ingredients, when added singularly (as in, yes, I had to start over many times to test this preliminary part) to the starting red cauldron, turned the cauldron blue/green/red/green/blue. With the minor exception I believe MY last ingredient was a 'revert' and screwed me up as it didn't fit the color addition sequence of the other ingredients. (I never touched it after realizing that, and didn't need it in the end.)
Bumroot = blue
Leafy Slorgblossom = green
Crushed Jurpleberries = red
Salt = green
Bronze Sansam = blue (revert)
2) I tested out a few color additions and came to find that I could not skip making green, but I could skip making black. My first task was to make the first purple, since I knew all too well how to change things from red to green to blue and back, etc. Some incomplete notes (but enought to get the gist). Toward the end it didn't take me long to get the hang of it.
red + red = green
green + green = red
blue + blue = green
red + green = green
red + blue = blue
green + blue = green
red > green > blue > green = purple
purple + blue = black
purple + red = black
purple + green = pink
black + red = pink
pink + red = black
pink + green = rainbow
rainbow + blue = black
rainbow + green = (wrong)
rainbow + red = swirly yellow-green
swirly yellow-green + blue = sparkly purple
sparkly purple + red = swirly silver-red
3) My final sequence involved 8 ingredient additions and went like so:
(start) red > green > blue > purple > pink > rainbow > swirly yellow-green > sparkly purple > swirly silver-red (end)
--- Aaaaand this probably helps no one other than people like me, trying to derive logic from color. *Flashbacks to crystals and tombs...*