I learned as a kid the distinction between white and yellow, which technically have the same runability, also as a function of visibility (and shade changing clear visibility).
So as a fun way to remember, we learned: if sunshine on a sunny day can reach your shoes (mowed grass, bare land, etc.) it is bright yellow; if the sunshine can reach you but not your shoes it is light yellow (usually tall grass), and if the sun can not reach you, but you can see far then you're in white. We further differentiated the same way for green stripes and full green: if it is in the way of your feet but not you eyes, then it is striped.
The canopy extension also comes into play when you have sprint maps with single large trees having a white area around a single green circle symbol on a big yellow lawn.
Tree depictions on Sprint maps
in Kell Sønnichsen's Sprint Mapping guide