Talk:Penny's Team/@comment-27087508-20151213044100/@comment-86.153.151.78-20160207182711

Actually, copper is very fitting for the two characters so far.

Allow me to give a very brief chemistry lesson here.

Transitional elements, of which copper is one, have a unique property compared to other elements, they are able to stabilise with different valencies.

To give a similar example, iron (Fe) has two different colours for iron oxide depending on this. FeO is green, but Fe2O3 is red, it is the latter that is present in haemoglobin, which gives mammal blood its characteristic red colour.

Copper-based elements can create a rich blue crystal, for an example, copper sulphate. It is also the key ingredient in blue stained glass.