To be clear, all species can sense it to various degree of precision, and of course trained magic user can sense the different mana in the air as Max does, as he can tell what mana is within the bomb just using his nose. Humans are the only one to have the ability to visually see it as colorful energy, and it is hinted that they have a innate flexibility when it comes to using it.
If human mana had a color, maybe white? because you know: white is all the color at the same time, human mana is about perceiving the entire truth...
a sum up of what we know here: