What the triggers apply are the default background settings from the Styles Dash (and current Theme Folder). These are easily overridden. To override these, simply assigning a value to the appropriate override attribute:

For example, if the default webpage background is #eee and I a note uses the BKG-COLOR trigger, its webpage background will be #eee (light gray). But if I set the color override attribute to #f00, the background will be #f00 (garish red).

Because every note has override attributes, every webpage can have its background set to an image, texture, or color other than the defaults set in the Styles Dash. These can be set per note, per prototype, and per website (in order of override). And by using the BKG-BEQUEATH option, they can be set per nuclear family (parent and children).

$blogBkgColor, $blogBkgTexture, $blogBkgImage, $blogBkgCardColor