One of the great things about succulents is how much their leaf colour varies over the course of a year. If you live somewhere with a nice range of temperatures and you keep your succulents outdoors you'll get to see the full range of beautiful colours.
A good way to visualise this is to show you my Echeveria Chrissy n' Ryan. All images in this post feature the same cluster I've had for about 4 years. This cluster has been with me a number of years and has shown me some great colour changes in that time.
Summer colours
The sun can bring out deep colours in the summer but sometimes it's tough to strike a balance between sun stress and the lighter colours that warm temperatures can bring out.
Above is my cluster not long after it was first purchased. Most of the leaves are the same colour with only a little pink starting to appear on the tips.
By the next summer there had been plenty of time to stress my cluster and this was the result.
The leaves are lighter overall with more uniform pink highlights showing through.
It can take several weeks to 2 months for change in environment to reflect in the appearance of your succulents. This means you may not know for some time if you aren't giving your succulents enough light to get stress colours.
Spring and Autumn
In Spring and Autumn the colours on my Echeveria Chrissy n' Ryan cluster approach full brightness and contrast. The pic below is from Autumn. Not only have the older leaves turned a bronze colour but the inner leaves have changed to a nice blue colour with pink and purple accents.
Here's another image - this one from spring:
Now it's showing a beautiful gradient of colours.
Winter colours
Finally, the strongest colours come out in winter.
The outer leaves contrast strongly against the inner leaves.
Once you're collecting succulents in the long term you start to notice all the seasonal changes and look forward to them every year!