Theming

Use monokai-pro palette while honouring fade-in if in effect:

(( $+commands[pastel] )) || riverctl background-color 0x1b1d1e
riverctl border-color-focused 0xa6e22e
riverctl border-color-unfocused 0x75715e
riverctl border-color-urgent 0xf92672

Todo

Theme definitions should really be configured more centrally, but for the time being it works.