Where can I buy hair level swatches?

They wouldn't be a lot of help TBH. The colour levels are pretty vague, there is quite a range of colours in each level.
Do you want it so you can ask for specific dyes? Each brand will vary, so  it is more a case of knowing a particular line very well (which is why most professionals stick to just a few brands)
What colour are you aiming for?

Thank you so much for your response! That's a bummer about swatches but I think I understand what you're saying. My last colorist told me that my natural brown is " a 4 or 5" but who knows what he's comparing that to. I haven't picked out the actual color I plan to buy yet but I'll attach a couple of pics of the general idea of what I want below - a deeper yet definitely not black, red purple.  I had medium red hair for years and got sick of it, went to a colorist asking for what I want and ended up with a purple-black color. It looked black indoors. I let it lighten up and he removed the remaining dark color to correct it - it got to a deepish ginger color for the base. I was in the salon for 8 hours. It looked great  (the color in my profile pic), close to what I wanted, but then ONE shampoo and it washed out. Now it's a dull, sickly light plum color with blonde streaks.

So, I really know nothing about proper application. I ruined my hair years ago by stupidly using level 20 all over my whole head every time I dyed to revive the red. My hair was gummy =( 

Looking for something along these lines. I'm flexible, but I don't want it to look black indoors and I don't want it super bright either.  These show both the lightest and darkest I'd want to go with some colors in between. ANY advice is appreciated. I don't know where to start.

Here's the color it is now. The light in here actually makes it look more vibrant than it actually is. WTH?! lol, kinda.

Honest
Y, all of those are going to end up looking pretty much black indoors. They have light on them in the photos so they look brighter. But look at the areas where the light isn't hitting. With the exception of the first one though I think that's mostly because it's a bright room, It's very dark. You lose a most of colour to the depth of the shade when you're not in direct light. It's just the way darker colours are. You either need to stick to a mid range colour or go darker and get over the fact it's almost black in less bright light.

I do understand that sometimes these color will look quite dark, but the previous salon color seriously looked blue black in almost all lighting unless you directly shined a light from a certain angle and examined closely. I was even very happy with the color in my profile pic (that's the color after it was corrected). The problem is that it almost all washed out in ONE shampoo. It was permanent die, so I was expecting a slightly better performance.

I found  a pic of directions dark tulip and I rather like (first pic). Trying to figure out what my base color needs to be in order to achieve and how to do that without frying my hair.

I suppose this would be considered mid-tone?

The second pic is the color I was happy with.

I would definitely go for a direct dye over that base, you will have more control over the final outcome and no further damage.
Directions Dark Tulip is a similar shade, but may be slightly too vibrant on your base. I would mix with something like ador Bordeaux which is a purple based brown. Alternatively do Bordeaux first, and put a magenta shade over the top.
If you want to create the colour entirely from scratch, a brown, a red and a pink based purple would be what I would buy.
For long lasting shades you can't beat Special Effects (Nuclear red and Deep or Pimpin purple)

You make a great point. I think I was seriously over complicating this, which I tend to do. Since my roots are only like an 8th of an inch, I should just go ahead and experiment with the direct colors now. I already hate it, so I guess the out come couldn't be worse than still just hating it with the direct dies. Actually, it HAS to be better. Thank you so much for the tips on color mixing. They're cheap enough, that I'm going to buy a few an experiment a bit.

I'll learn how to lift my roots properly when I cross that bridge!