List of Elements and Subtypes.

This is not a complete list - More elements might be added as they are discovered, along with info about powers, mutations and colors.

Fire - One of the oldest elements, Fire is also one of the most powerful - having the basic ability to create and control fire in all forms. Colors range from light yellow to deep red, blue and white rarely appearing as well. Common mutations include lion tails and mane and tails made of flames. Personality wise they are generally aggressive, short tempered and sort of competitive.

Spark - A rare element that is almost identical to Fire. It is a mystery when where and how Spark became an element unto itself, but it is. Direct fire-controlling powers are limited however they can create fire any where they want, even under water. They also have limited control over light. Common coat colors are yellow, orange and red with yellow being dominate. Sparks are often seen with sparks of light and fire flaring from their manes and tails constantly, sparks may fly from their hooves as they walk. FYI, these sparks are harmless unless they are intended to do harm.

Smoke - A semi-rare element that descended from Fire, colors range from white to grey to black with red and orange being common as well. They seem to be able to create and control smoke, and mist from time to time as well - handy for escaping predators and sneaking up on others.

Earth
Flower
Water
Air
Cloud
Metal(Gold or Silver)
Aurora
Rainbow
Season(Spring, Summer, Autumn, Winter Subtypes)
Draco(Wyvern subtype)
Demon
Darkness
Light
Storm
Dance
War

Mech(-anical) - Some argue that this isn't even a really element. Perhaps descended from Spark or Storm they can the ability to effect electronically devices and in some cases control them. There is no set color range, though blue, grey and red are mostly seen, and they often have mechanical limbs or armor

Ghost - are always seen in shades of white/grey, and sometimes green, no other fur color is unknown except for rare mutations and those with mixed blood. Those of this element are constantly hovering a few inches to a few feet off the ground and can temporarily increase/decease the distance between them and the ground at any time, to escape danger and such. Some of this element can even 'phase' through objects as a real ghost would. Mutations are rare for this element.

Vampire - call such because of their vampire fangs, gothic attitudes and ability to summon and control vampire bats. Common coat colors are black, grey, red, purple and orange; white is not unknown either. They mostly drink blood, but can eat all normal foods as well.

Star
Sun
Moon
Dream(Nightmare subtype)
Life

Animal - Totem would be a better name for this element. From birth those of this element have an affinity with a certain animal and will either be born with mutations linking it to the animal or will wear symbols of that animal (feathers, paw print tattoos). They can talk to most animals and project emotions to animals. They are highly respectful of nature and animals and as a rule do not abuse their powers.

Holiday - When a pony with a certain coloring is born on or close to a particular holiday associated with their colors they become this element regardless of the element of their parents. Not as a rare element as was first thought, however due to the nature of the genetics involved, mixed elements involving this element are very rare and far between.  Attitude, coloration, and powers largely depend on holiday and the parent's elements, as a rule of thumb a Holiday will have the colors of its represented holiday as the majority of its coloration and at the very least powers similar to it's parent's as well as powers associated with the holiday in question.
Quick run down of the major and most commonly seen Holidays:
Easter - pastels, 4th of July - red, white and blue, Halloween - black, orange and sometimes green, Christmas - red, green, white and sometimes blue.

Dawn
Night
Twilight(mix of Dawn and Night)
Wind
Wisdom
Wave
Hope
Death