From Wikipedia:

"Niobium, formerly columbium, is a chemical element with symbol Nb (formerly Cb) and atomic number 41. It is a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite. The name comes from Greek mythology: Niobe, daughter of Tantalus since it is so similar to tantalum."

Small amounts of niobium are added to steel to drastically increase its strength, to make superconductors and in jewellery thanks to it is hipoallergenic.

However, the thin film oxide that grows on the surface of the metal during anodization produce gorgeous colors.

And what do you need for anodization?

- A metal to be anodized connected to the positive of the power supply --> Niobium

- A metal that cannot be corroded connected to the negative of the power supply --> i.e. stainless steel

- A power supply up to 120 V and able to deliver at least 3 A.

- And finally an electrolyte where the metals can be immersed. In this case...diet coke????!!!!! --> Yes, because it contains phosphoric acid that it is mainly used in the anodization industry.

With all these elements and just changing the voltage you can obtain the following colors (from left to right and from top to bottom, beginning with 5V and 5V steps):