"How can I achieve swipe gesture gradients in Illustrator?"
For a better reading experience, I would recommend visiting to Quora for my original answer.
So the other writer, BMX, had a pretty cool and creative approach to the question as well. But to approach it the way your image had, it most likely was the Blend Objects method at work.
It’s not too terribly complex, but there are a few unique twists depending on the blending style and method chosen. There are also a few parameters to adjust when it comes to the blend result as well.
So let’s start with the simplest one—a two-color blend.
Make 2 circles, each filled with a different color. Remove the stroke, if any.
Select both circles and hit Ctrl/Cmd+Alt+B to initiate the blend. You can also access the effect by going to the Menu>Object>Blend>Make.
Once you have made your Blend path, use the Direct Selection tool (A) to adjust the Blend path as you would any normal path.
Now, what if you wanted to replace the Blend path with, let’s say the number 2 like I have above?
To do so, simply select the entire Blend Objects group and the path that you want to replace it with.
Go to Menu>Object>Blend>Replace Spline to replace it with the newly selected path. Keep in mind that the location of the blend group will update to the new path, and the scale of the blended objects remain the same, so make sure you got those things right where you want them.
There are other options available in the Blend Menu as well, be sure to check them out to see what they do.
To make a multi-colored blend like your original example, we’re gonna have to break our blend down into segments and approach it from there. It’s a lot simpler to show it than to tell it, so I’ll try to be conservative with my words and show you the essence of it so you can experiment with it yourself. Hopefully, it’ll make more sense below.
A few things to keep in mind here. Objects in Illustrator have an arrangement order (or z-index for you 3D and web designers) and that order is still in place for the objects within the blended path as well.
Basically, the circles themselves have different z-index orders which affects how the blend behaves.
The entire Blend group as an entity has a separate z-index order that affects how it interacts with other Blend groups.
The reason I’m mentioning this is because it will affect how the final result will look:
Hopefully, this should give you a general understanding of how blending works. As I have mentioned before, there are several parameters and tweaks that can be adjusted depending on the intended result. It’s probably better if you play with it to wrap your head around the concept. It’s pretty easy once you get the hang of it.
Best of luck!
