I'm currently painting a bunch of 20mm British Paras and thought it fun to contrast my current painting style with my style from 17 years ago. I found two of the same figure pose, one of which I painted yesterday, the other in 1998. Here's them side by side:
The figure on the left is the recently painted one. You can see there has been quite an evolution in my painting style.
The most obvious difference is in the colours of course. Back then I used a combination of Tamiya and Games Workshop paints, nowadays I use Foundry triads (well, diads, as I only use two layers per colour).
Other differences are more subtle, but one other obvious one you can see is that the recent figure is painted in a much bolder style with stark colour contrasts and sharp delineations of colour areas, whereas the one on the right is (except for the face) much more 'natural'.
One other difference which is not obvious from the photo is that the figure on the left took only a quarter of the time to paint than that on the right. And that is of course the reason behind this evolution of painting style: get many painted figures on the table, designed to look good on the table but not necessarily in close up.