The thing is, she may "know" what the units involved in electricity are and how they relate, but she doesn't know in terms the crystals understand. There will need to be a good chunk white involved to pull that information from the ether and regulate everything safely.

Red can totally do lightning, though. In a bursty sort of way. Green can too, but more in a sustained way? Better for charging batteries at least. Blue can't really help here... Well, a LOT of blue could give her the ability to withstand lightning strikes and convert it into whatever red and green are doing as more juice?

Hm, she wasn't expecting green to pipe up and that suggests she doesn't thoroughly understand the specs of the colors.

She checks but she does not actually have a convenient chart of how many electrons go into how much voltage or anything like that on her local storage.

She assumes but would be remiss in not checking - presumably it'd be vastly more expensive to have the ability to revert things such as her everything to previous states (worse for notetaking, but very widely applicable)? To create or act as a solar charger? To make the everything work without electricity at all?

Revert things such as her everything to previous states: VERY expensive and limited, takes white and black and red.

To act as a solar charger: Still some white, and some blue.

('Creating a solar charger' gets some sort of reaction from black and white, but it feels underspecified)

To make the everything work without electricity at all: Lots of white, bit of green.

(What will he need to invent things? A good memory? Steady hands? The filter ball is a good start, and being able to read foreign books too, but he just doesn't know...)

Okay, scratch all that then, she's got limited capacity. Green, low-level sustained electrical charge generation that'll charge her everything and... make her zap people or animals who touch her if she's got it up? Like, at least enough to keep bugs off and discourage people nonverbally inquiring if she hooks on the side.

Yep, a whole green can do a fairly deterring amount of charge, and half could do 'bug zapper' level, sustained for long periods. She'll still need a lil bit of white to successfully charge the everything.

A smidge of white is fine. She doesn't necessarily need to kill bugs that approach, just make sure that in this preindustrial world she's really inhospitable to parasites and anything carrying diseases, so she can settle for a pretty low level, she thinks.

The low level she's thinking of is 1/3 green, 5%ish white.

Yeah that seems fine. Ker-magic.

Shiing! The sense of warm stretching is maybe fading more slowly this time. 

"I'm definitely noticing the having had a lot of magic, I should slow down. Maybe we want something to get the donkey up and moving but that can wait till we see if giving it water does the trick..."

"He's probably just tired?"

He's still wiggling the filter sphere around. The air feels kind of dry now, and there's a couple inches of water at the bottom of it.

"I want one of us to use the yellow one. For healing. In case the mountain lion attacks."

"Maybe we should design a power for it now, but which of us gets it should be whichever is in a position to use it, if we do wind up getting hurt."

"I think injuries are more time critical than infections but probably it should help with both."

"They're pretty different, it might be hard to get one efficient power that does both."

"There's some diseases that aren't just bad germs, too..."

"What kind do you have in mind?"

"Miner's lung or pellagra. Oh and hatter's disease. That one is because mercury is poisonous, not because of hats. But hat makers used a lot of mercury. Mrs. Wilhelmina Gearing found that out with magic and wrote it in a book."

"...well, I'm hoping to avoid poisoning in the first place, which sounds easier than avoiding injury."

"Probably injury is more dangerous right now."

"Yeah. Also I trip a lot, so it'll be nice to have something for the bruises and sprains I pick up all the time, which I guess is a reason for me to be the one with the healing power."

"...Didn't you just use magic for not tripping?"

"- you're right, I did, I'm not used to it yet."

"I'm scared of being hurt and not being able to fix it. My dad is evil but he was right about one thing. You can only rely on yourself in the end. I want to have the healing magic."

"Okay. Unfortunately everything I know about biology is about Amentan biology, not yours, we look similar but I don't know how surface-level that is."