
"That's not the color in the bottle".
That was my first thought after I had laid down this new color. I saw this color online, and I was like, "In my basket, NOW"! I arranged the whole color palette around this one, GOR-GEOUS looking color.
I got it. Immediately set myself up to paint - but when I poured the color onto my palette - it looked....off. I laid down the color and, "What the hell?!"
One of these variations of phrases came out of my mouth with every color that has been different from expectation - or different from what was advertised:
This color looks duller than in the picture...
Why is it so streaky?...
GAH!This stuff is THIN. This is gonna take forever to get full coverage...
And then, one night, I was watching The Devil Wears Prada and got a glimpse to the solution I needed. I needed a color swatch book.
So I purchased thin sheets of white & black leather from an Etsy Store.
Why white & black?
Because when paint covers them, they give off different hues of the same color. So if you put red on white, it's the true color that comes out of the bottle. If you put red on black, the color will come out slightly darker than the color that's in the bottle. When the sheets came in, I cut them up into small squares. Let's say 1.5"x 1.5".
I then took each color that I had in my arsenal and started to paint the squares, leaving a small corner untouched by the paint. Each square got (3) coats, drying them with a hair dryer in-between coats.
Three coats may sound like a lot, but it took me no more than 3-5 minutes, each square.
After it's dry, flip them over, and place a piece of masking tape on it with the name & brand of the color. If you want to put another quick note on the back like, "Streaky" or "Don't Use"- go for it.
That little corner that was left untouched was there so I could pin the leather to a cardboard wall, which I did for a long time.
When you're done, you'll be able to see which colors/brands are - hard to work with, which are REALLY thin, which ones are opaque, which ones are streaky, and so on.
You'll also be able to pull the colors from your mosaic and determine which colors will work well together for whatever you're trying to paint.
Doing this takes the guessing game out of painting your sneakers. The excuse of "I didn't know it was gonna be THIS color" or "I didn't think it was gonna be this hard to work with" goes out the window. And that's because you did the prep work beforehand.

(image from socialprintstudio.com)
As far as where to store your sample sheets - you can:
post them onto a cardboard using thumbtacks
place them in a tiny photo book
you could punch a hole in the corner of each sample, and attach them with a ring you purchase at your local craft store
And so on.

Either way, make sure it's simple for you to take the sample sheets in and out of its spot, or you'll get annoyed, and eventually give up on using it.
And that's it. It's a simple solution to a problem in the beginning stages of me painting sneakers & hopefully it'll be a solution for you as well.
Now go forth, mix & match colors, and find the color palette that will match the "mood" you're going for.