I use element not in the periodic table sense, but fire, air, water, etc.
I am trying to create a world with 6 main elements, based on primary and secondary colors. Red (fire/heat), purple (air/steam), blue (water), green (growth), yellow (earth), and orange, which the best option I have been able to think of is either lava or metal.
Lava is the more natural feeling choice, but I can't think of enough aesthetic characteristics that would distinguish a lava plane from a fire plane. Metal is an easier design choice, but I am having a much harder time justifying it as the intermediate element between heat and earth.
EDIT: I've taken a lot from many of the comments and answers, so I want to put up a sort of modified state, and elaborate on some things that people have noted in their responses:
- Yellow - earth (sharp, cold, slow),
- Green - nature/growth (dull, hot, slow),
- Blue - water (dull, cold, fast),
- Purple - Air (sharp, cold, fast),
- Red - Fire (dull, hot, fast),
- Orange - Metal? (sharp, hot, slow),
- White - Light (ether - sharp, hot, fast),
- Black - Dark (void - dull, cold, slow), and
- Center/Colorless (chaos)
Further combinations of any adjacent elements will likely be possible, but I am not certain if they will be strictly defined. Dark + fire = famine (Henry Taylor), earth + darkness = decay (Xavon_Wrentaile), light + growth = life, dark + air = curse, etc.
EDIT 2: This also isn't to say that there is a hard connection between light and good, dark and evil. For example fire + light could be blindness, air + light could be lightning (which I perceive as an almost exclusively destructive force). My intention isn't to conflate elements with intention, though character personalities will likely have some basis on their attunement (fire might tend toward brash, nature towards serene, and the like.
Attempt to clarify question: What is an element that has the attributes sharp, hot and slow that could logically be placed between Fire (red) and Earth (yellow) in a magical spectrum?