Hey folks - I've lurked about here for awhile, finally got the gumption mustered to sign up - figured I'd just jump in and wade into an aspect that isn't "The Fun Part", but can make "The Fun Part" go a little bit smoother - a dye recipe book. This is less about a particular color than keeping track of the results of color mixes, so...if this has landed in the wrong spot on the forum, feel free to nudge it elsewhere. I figured the best way to see how other people might handle their recipes is to start off with a post on how I muddle through with it, too ;^)
I use Fuschia, Lemon Yellow, Turquoise, Cobalt, Sky Blue and (dharma) New Black, and mix most other colors from there. Mixing from powder worked well for me, it just got rather time consuming when dye sessions starting requiring upwards of 2 dozen colors - that's a lot of shaking teaspoons around. Having 'stock' concentrations of the main mixing colors in liquid form and combining from there saves a lot of time, but I found myself getting kinda lax in the reproducibility department...Tuesday's Royal Blue and Thursday's Royal Blue would resemble each other, but there would still be more variance than I'd like to see...thus the recipe book.
The scrapbook-ish amongst us may have some much better suggestions for this, but for the book itself I just picked up a 3 ring binder and printed out templates from a word document and stapled swatches. The template itself isn't too detailed, but has a place to put the color name, the measurements/ratios used to create the color, notes & general thoughts as well a spot for noting the color's cast and edge/bleed.

The swatches themselves are cheap muslin with an accordion fold ran down it.

Not exactly intricate, so half the time I don't even bother tying a knot. Scrawled abbreviations in a corner of the swatch with a sharpie works for keeping track of most colors, but some other approach would be much better on dark tones. (what that other approach that might be, I have no clue...but there's gotta be a better way)
I only dye one side of the folded swatch - this allows for a pretty good fade/bleed on the small hunk of cloth and compares well to how the color will look on an actual tied item.
One thing that became clear with the first round of attempted swatches made by combining liquid dyes was that scaling between the amount of dye used to fill a bottle and the amount used to make 1 oz for testing purposes...was that cups/ounces/tbsp/tsp measurements realllllllly got on my nerves. It might be different if you spend more time in the kitchen than my 'toast and pizza rolls' culinary abilities allow for, but for me it got a little mind numbing to scale multiple liquid ounce measurements down to fractional teaspoons and keep the ratios exact. Considering the dharma squeeze bottles seem to actually be made in milliliter increments, switching to metric made a lot of sense - creating a 1/10th size run for testing purposes was just a matter of shifting a decimal point.

Picked cylinders up off of amazon, but if you've got art or teaching supply stores in the area, they may be worth trying as well - 1000, 500, 250, 100, 50, 25, & 10 ml came in a set. the 10 and 25 are very handy for test mixes, the 250 and 500 work well for filling bottles. Even if these weren't more convenient than using spoons and measuring cups, they would still add to the mad scientist vibe of the whole affair, and that is its own bonus

Plastic bathroom cups are a good size for test runs (most are around 3 oz / 90ml capacity), altho a 4 by 5 swatch accordion folded can be dyed with an eyedropper with around 10 ml of dye liquid. The waxed paper cups will work, but only if you're going to immediately use the dye - after an hour or two, things go a bit soggy.
A good starting place is your primaries, and primaries at different dilutions. For examples sake, Fuschia (2 tbsp of dye/1 cup water), Lemon Yellow (2 tbsp/cup), Turquoise (4 tbsp/cup), Sky Blue (3 tbsp/cup), Cobalt (3 tbsp/cup) and New Black (5 tbsp/cup) - for each color, I did full strength, and then 4 dilutions (50%, 25%, 12.5%, and then an extreme dilution made from 4 squeezes off of an eye dropper into 8 oz of water)

From there, if you're just looking for a simple spread between the primaries, a quarter step rainbow can give you a reference for the basic ratios between the colors you're mixing with.

The top row for example is 100% lemon yellow, 3/4 yellow 1/4 fuschia, 1/2 yellow 1/2 fuschia, and then 1/4 yellow 3/4 fuschia...the other rows follow suit)
For a little more detailed range between two colors, I do a 10% gradation - in this example, it's 100% sky, 90% sky 10% fuschia, 80% sky 20% fuschia, etc.

on the left of each page is full strength, the right is a 50% dilution - the 2/3/4 and 5 tbsp of dye to water ratio works well for initial mixing volume, but other than accents I rarely use dyes at that concentration. 50% or even 25% dilution is more common and for a lot of colors still delivers quite a punch. For small swatch purposes, a 50% dilution made from 5 ml of dye combined with 5 ml of water (or 1 tsp each) is enough if using an eyedropper or syringe, so while having dilution examples of your mixes may mean you have a workspace cluttered with lots of little cups for awhile, it doesn't have to go thru much dye.
Having a spreadsheet to summarize stuff helps, too - I keep a printout of the recipes for each color range at the beginning of that section in the binder. For me, 250ml was a basic volume, so I kept that as a standard end result of the mixes - halving/doubling/etc when making the dyes for actual use is fairly common, so taking that into consideration kinda made sense.

Well...that's how I'm trying to put together a binder of short term memory, and hopefully an introduction of sorts - any suggestions or descriptions of how you keep track of things?