With the introduction of ads and a new timeline to make sure you "see the moments you care about first", Instagram has undergone a logo and interface change. The logo is a simple rainbow design and the interface is merely black and white. Their thought; make it more about the photos and videos. My thought; people didn't like the ads and timeline change so they want you to feel like they're doing something for users.
While the minimalist look actually does offer a less distracting view on your screen, it doesn't really change a whole lot. If you've made the update to you can see the changes for yourself or check out the promo video above. If you are an Instagram user you can always follow me and see what I'm up to HERE