Chromatic Bloodline

At some point in your family's past, they made contact with a creature of the elements, changing the course of your life. Using sorcery points you can alter the damage type of certain spells.

Elemental Affinity

At 1st level, you choose one type of element that has tainted your bloodline from Acid, Cold, Fire, Lightning, or Poison.  
You can speak, read, and write Primordial. additionally, when you make a Charisma check when interacting with elementals, your proficiency bonus is doubled.

Dynamic Elements

Starting at 1st level, when you cast a spell that does Acid, Cold, Fire, Lightning, or Poison damage, you can change the damage type to your chosen bloodline element by spending a sorcery point.

Elemental Resistance

Starting at 6th level, you gain resistance to your bloodline type. If you already have resistance, then you gain immunity. 
Additionally, you add your charisma modifier to the damage rolls to any spell that you have changed to your bloodline type.

Elemental Blast

Starting at 14th level,  At a point, you can see within 60ft of you, you can cause an eruption of elemental magic. It has a radius of 15ft and does 3d6 damage of your bloodline type. you can spend one or more sorcery point to increase the damage by 2d6 to a maximum of 9d6. You regain this ability after finishing a Long Rest. 

One With The Elements

Starting at 18th level, you no longer have to use a sorcery point when using your Dynamic Elements feature to change the damage type of a spell. You also gain immunity to your bloodline type. Additionally, as an Action, you can target up to six creatures within 30ft of you and grant them resistance to your bloodline type for 1 hour.