Kryptonite

Kryptonite is a radioactive mineral from the planet Krypton. Following its destruction, some Kryptonite found its way to the planet Earth.

Green Kryptonite
Kryptonite is normally green and Kryptonians exposed to the element will become weak within close proximity or pierced by weapons laced or made from the substance, and prolonged exposure to the element for Kryptonians is fatal. Kryptonite's effects is radioactive in nature and therefore cannot penetrate the element lead. The radiation of the mineral can be harnessed and used independent of the mineral itself to harm a Kryptonian, usually appearing in the form of artificial light emitted from certain machinery. Alex taught Kara to fight in a room lined with low-intensity Kryptonite emitters, just enough to be brought down to normal strength. Alex Danvers utilized a sword made from Kryptonite, and it was ultimately used to kill Astra. Physical signs of being affected by Kryptonite are somewhat fever-like, including nausea, weakness, dizziness, vertigo, fatigue, pain, and loss (or near loss) of consciousness. Physical contact with Kryptonite of higher intensity is enough to cause burning pain. It has even been used as anesthesia or a sedative against Kryptonians due to its affects. Kryptonite inside the body causes green glowing veins to protrude from the skin of the Kryptonian and the physical pain it causes becomes unbearable at that point.

Blue Kryptonite
The blue, molecular opposite of green kryptonite and was created by the D.E.O. by reversing the ionic charge of green kryptonite. It was used to subdue Bizarro. While it had no effect on Kryptonians, it severely weakened Bizarro and sedated her, allowing her to be captured and then put in a coma. It also seemed to have a calming effect on her, removing her rage toward Supergirl, causing her to accept the need to put her in a coma and ask for forgiveness for her actions. Therefore, it effectively made her more rational and understanding towards others, something she struggled with before.

Red Kryptonite
Maxwell Lord created a synthetic red form in hopes of subduing Non's next attack. Rather than weaken a Kryptonian physically, Red Kryptonite alters his or her mind by weakening and gradually destroying their inhibitions, as well as bringing out every negative thought to the surface. They can even feel its effects long after they have left its presence. As this happens, red, glowing veins momentarily protrude from the skin when they first come near it and in times when the victim's actions and thoughts are most affected by the Red Kryptonite.

Silver Kryptonite
A silver colored form of Kryptonite that was found and used by Queen Rhea from the vast quantities of Kryptonite that rained down on planet Daxam. This kryptonite will cause a Kryptonian to fall in a deep and frightful hallucination where nothing from the outside world will stir them out of it until it leaves their system.