A few quirks with styling an <amp-sidebar> within an <amp-story>. (Tested on Chrome and Safari, AMP version 1904200955460.)

(Desktop only:) A 100vh child <div> of an <amp-sidebar> is not full height:

(Expected: the green border runs the full height of the page; CSS is amp-sidebar div { border: 3px solid green; height: 100vh; }.)

Source: https://gleaming-crepe.glitch.me/.

(Desktop and Mobile:) It's not possible to set the background-color of <amp-sidebar>:

(Expected: sidebar has red background; CSS is amp-sidebar { background-color: red; }.)

Source: https://pollen-snapper.glitch.me/

/cc @newmuis