Mage Sight

Mage sight is available to races with a fey background, as well as to Artificers, Sorcerors, Warlocks, and Wizards.

Mage sight allows characters to see the energies associated with magic. 

This functions (predominantly) as a detect magic spell:  While seeing the presence of magical energies does not indicate the school of the magic, the color of the energy can reveal the source (arcane, divine, shadow, fey, fiendish, etc.) of the magic, and the brightness is usually a guide to the relative strength.

Under certain circumstances (DM's discretion), the use of mage sight may bestow advantage to a character attempting a magic-related skill roll or ability check.