Chromatic Orb

Chromatic Orbs are primarily used to change the colours of sockets on an item. Sockets are more likely to roll a colour corresponding to the attributes of the equipment being altered. The higher the attribute requirements, the more likely it is to roll the relevant color: red sockets for Strength, green sockets for Dexterity, and blue sockets for Intelligence. It's only possible to get red, blue or green sockets using this orb; for white sockets it's necessary to use a Vaal Orb.

Chromatic Orbs can also be obtained by vendoring an item with one socket of each colour linked together. This is one of the most common ways to obtain Chromatic Orbs. In particular this means you can get some Chromatic Orbs cheaply (typically for about one Orb of Transmutation each, or less) by buying such linked items from the Vendors. If one either wants to avoid randomness, or wishes to obtain a specific colour combination that is unlikely on a certain item, one can instead use the Crafting Bench recipe found in the Delve mine.