Chromatic Combatant

The Chromatic Combatant focuses on versatility above all else.
It has a few uses of its key feature and they last for a full round of combat so don't be stingy.
You also get them back at a short rest so don't worry about running out.
Find a weakness and exploit it or just get past those pesky resistances.

Chroma Combat

At 3rd level you gain the ability to shift the damage of you weapon from its original damage type to a new one.
When you get this feature choose three options from the six below, at 7th, 10th, & 15th level you gain access to one more.
Acid, Cold, Fire, Lightning, Poison, & Thunder
As a bonus action on your turn you can activate this feature, it lasts till the start of your next turn.
You can use this feature equal to 1/2 your fighter level (rounded up) plus 1, regain all uses on Short/Long rest.
Chroma Combat also gives you increased damage well active. 
Lvl 3 - 9th: +2
Lvl 10 - 14th: +3
Lvl 15 - 19th: +4
Lvl 20:  +5

Expanded Chroma

At 7th level, & 10th level you can add either necrotic or radiant to your Chroma Combat damage types for free.

Enhanced Chroma

At 10th level each of your Chroma Combat damage types have an extra effect. Save DC = 8 + Prof + Con
Acid - Creature makes a Dex saving throw, on a failure the creature takes the 1/2 the damage again at the start of its next turn.
Cold - Creature makes a Con saving throw, on a failure the creature has is slowed by 10ft and has disadvantage on the next weapon attack it makes till the end of its next turn.
Fire -  Deals an extra 1d6 damage, and sheds dim light 10ft.
Lightning - One creatures within 10ft of the original target makes a Dex saving throw or takes the damage as well.
Poison - Creature makes a Con saving throw , on a failure the creature is poisoned until the end of its next turn.
Thunder - Creature makes a Con saving throw, on a failure the creature is pushed 10ft away from you, on a failure of 5 or more the creature is knocked prone
Necrotic - You gain temporary HP equal to the damage dealt.
Radiant - Creature makes a Con saving throw, on  a failure the creature is blinded until the end of its next turn.
Psychic - Creature makes an Int Saving throw, on a failure the creature is stunned until the end of its next turn.
Force - Your weapon attacks are guaranteed hits.

Mind Match

At 15th level you gain get to add psychic and force to your Chroma Combat damage types.

Countless Chroma

At 18th level you have unlimited use of the Chroma Combat feature.