I am making .kml-files to visualize measurements. I have defined a few styles and depending on the level of a given parameter, the points are plotted with different colors. The legend is put in the file-level description of the kml-file. Here I have used a <ul> to get the points for the legend. Each <li> has a specific style to have the right color on the dot. To avoid having the text in the same color, the text within the li is put in a <span> having the color set to black.
e.g:
<li style="color:#ff0000">
<span style="color:#000000">> 6000</span>
</li>
gives this text:
- > 6000
An example kml file can be downloaded from here. The php-file used for creating the kml-file is here. The latter file is made for a specific apllication, but I hope it may work as a starting point for others. And – yes I know how to do oop in php, but I did not find it useful in this fairly simple script. The legend may also be put into some kind of overlay on the kml. More investigations to be done.