Its always about the colors. What color should it be, how will it feel, and (most importantly), will I wear it? Color is always my first consideration when choosing a yarn for a project. I am rarely driven by a fiber type so much as by what shade it is, how it fits into my wardrobe, the intended season.
For the Hot Lava Cardigan, I envisioned a minty green, like Altoids Spearmint:

However, preliminary tests involving Kool-aid dyeing did not quite yield the right shade. The closest I got is evidenced in the sample second from the right in the top row, below. In real life, it resembles that aqua shade often found in acrylic yarns destined for baby garments. oh no.

From left to right and top to bottom, they are in order of dyeing. The colors that turned out the best are the ones I did last.. guess I got the hang of mixing by then!
There were a couple shades that stood out for the Hot Lava Cardigan.

Not-so-Muted Pink. This was 2/3 pink lemonade, and 1/3 lemonade. Could be muted down further though, in person it seems very bright. Perhaps by adding a little tiny bit of green.

Duck Egg Blue. Equal parts blue and green, plus a shake of grape. This is like my go-to color. I am always drawn to it.

Straw. 2/3 yellow, 1/3 orange, plus a shake of grape. I loved the variation in this shade, but wondered about the wearability of the resulting garment.
Following a great deal of deliberation regarding color choices, I decided on muted pink. But, after mixing up an entire dye pot of just the right shade of muted pink, at the last minute I poured it out and went with Duck Egg Blue.

The dye pot is a 21-quart canner I purchased from Kmart for $20. It worked quite well for these 3 skeins(5oz each). They fit with no problem, and I probably could have added another skein too.
The final result is not the blue I expected, but I am very very happy with it. Its like a seafoam green, a darker variant of spearmint green.

The Kool-aid recipe:
4 Flavoraid Lemon-Lime*
5 Berry Blue
5 Raspberry Reaction (also blue)
3/4 packet Grape
1/2 packet Orange
*Flavoraid Lemon-lime seems MUCH more potent than KA green. It only took 4 packets of it to 10 packets blue! It also seemed to penetrate the skeins unevenly, leading to some lovely variation.