Instructor: First, select the rectangle tool. Click and drag while holding down shift to create a perfect square. With our square selected, we're going to come down here to these two overlapping squares, which represent our fill and stroke color.
To change our fill color, I'm just going to double-click on this top one. As you can see, our color picker comes up here. For our first color, I'm just going to pick a nice dark blue here. Hit OK, and now, you can see that our square has changed to that color.
I'm now going to remove the black outline around the square by selecting it, hitting X on the keyboard, which brings our stroke color up to the front, and then hitting slash, which removes it completely. I'm now going to duplicate our square by clicking and dragging, while holding down alt.
If I then hit command-D, it repeats that action over and over. We're now going to select our last square, and change the color this one to a light yellow. Now, we're going to select all our squares, go up here to the menu and hit edit, edit colors, and then click blend horizontally.
Now, as you can see, we've got a nice blend between these two filled into our three squares in the middle. We can now select all our squares, come up here to our swatches panel, and click this button for a new color group.
This brings up an options panel, where we can rename our swatches blue, blend, one. Now, you can see it's made a new folder with those swatches saved. Even if I delete these, we still have our color saved in our panel.
I can now make a bunch of random circles and fill them in with our swatches colors that we already saved. Because these colors are all from the same blend group, they feel like they fit together. This gives us a quick way to build harmonious palettes that we can then use in our illustrations.
When I'm making an illustration like this "Space Invaders"-themed one for our Redux course, I'll use the blend mode to find things like this range of purples, that I can then apply to the shading on a joystick, to a range of darks that I can use as gradients on the background, or between two my primary colors, like this bright green and blue that I used on the Space Invaders.
This helps add variation to your colors, while also keeping everything cohesive. I'll often use this technique to build a simple grayscale range from black to white. I really like starting my illustrations this way, because it forces me to think about value contrast, instead of shiny colors.
Once you've set up this range of values to pull from, you can play around building shape compositions that have a clear balance of lights and darks.