You have probably noticed how gradient colors have been recently trending, and honestly for some time now, and they are used in many occasions. Icons, screenshots and logos, you name it, they are using it. Gradient basically means that colors are blending together in a certain way. In other words, with gradient colors you cannot accurately say by only using your vision, in which point the colors are changing from one to another. Along with many other trends which have been trends back in 80s or 90s, the gradient trend has returned from that period of time as well. It wasn't used the way it is now, but in all its modesty, it was a trend back then. It is weird to think that all those trends from decades ago, are now back in everyday life. Especially multicolor blending has become a large trend, which means that there are more than two colors to blend together. There are many benefits in gradients. Not only do they make an image, logo or icon more interesting, it kind of creates a 3D effect as well.
Popular colors to use in gradient
Blue, cyan, purple and pink. Quickly scanned, fro primary colors, red and yellow are not that popular, and from secondary colors green is left outside alone; all this at least on the dominant side. They might be used as very fade ones in the palette, but the first four colors mentioned are more on the dominant side.
Association to certain apps
Instagram is one of the biggest apps overall and it also uses gradient in their icon. In fact, Instagram is such a big platform, that any app that has the same type of icon, can easily be associated back to Instagram. Not to mention, many icons are using the exact same coloring as well; blue, purple, yellow, orange and pink. Is that a bad thing? Not particularly, because people could associate the app being connected in a way to Instagram and if people trust Instagram already, the probability to trust the other app as well is high. As you can see in the picture above, the color scheme of the two are so similar - not to forget the white icon they both share. The only difference is the round corners and connected border in Instagram's icon. Even though the color scheme seems identical, not one color is exactly the same. But with only looking them through your eyes, they seem identical.