I had to ask someone at my first DFRP Game this question and she described her character's elements: Gas Liquid Solid Energy Plasma. Her boyfriend had done the same but his character had a chemistry degree just like he did IRL and classified elements by metal and metalloids and stuff as well as with real physics terms. I decided to be a homeopathic focused practitioner and channel anything I'd been able to mix with a drop of my own blood and used blades of gator aid to cut up ghouls cause it comes in pretty colors.
Fire Air Earth Water and Spirit are standard because Harry sees it that way and he was trained by "oldskool" European pinheads like Ebenezer and Justin. Harry thinks blue is defensive and his left hand is used for drawing energy in and his right is for projecting it.
Ramirez uses water magic but it's really a set of disintegrating green lasers and force fields that Harry calls water because water is about entropy and death rays are like super entropy.
My brother describes one of his wizards as using water earth and air because spirit and fire are too vague and insubstantial for him.
The schools are just a way of describing how you see the world and what you can't do rather than what you can. They could be animal vegetable and mineral. They could be 'Meat, Dairy, Grains, Fruit and Other (coffee and chewing gum.)
You could channel water as real water.
Or as green death rays.
Or as water made from ectoplasm from the never-never
Or conjure masses of Jello.
It's POST MODERNITY PEOPLE!
(as long as your dm and table mates say yes.)
Edit: I used strike through instead of spoiler. my very bad.
