Thank you so much for this concise yet informative class. I'm quite happy that you didn't spend any time on colour theory because I can get caught up in overthinking my decisions when I focus too much on colour theory.
I thought I would add some process photos here to show how I ended up with this somewhat muted colour palette for a summer theme.
Step 1 was finding an appropriate photo and selecting colours that appealed to me. At this stage, I was undecided whether to use a purple as my dark colour or whether to use a dark red. I think a palette with the red instead of the purple would be good to try as well.
Step 2 was seeing how the colours worked together. I felt that the orange was a little bright and conflicted with the purple and aqua, and that the light cream and pale blue were too similar in tone.
Step 3 was adjusting according to the above observations. I made the purple darker, desaturated the orange, increased the saturation of the blue, and adjusted the hue of the cream.
Step 4 was applying it to an illustration. I really liked the example of combining florals with ice cream, but I always remember getting cheap popsicles on sticks during summer when I was a kid, so I went with a popsicle stick and framed it with florals. You can probably see that I made use of Procreate's symmetry tool to sketch the the floral frame, but I inked each element separately and added slightly different leaves in order to reduce the pure symmetry of the frame.