Elgg 1.9 Themes -

Two specific files control the landing page experience for logged-in and logged-out users. Essential Files for Theme Development

Create a manifest.xml (or elgg-plugin.php in newer versions) to define the theme's name, version, and author. CSS Customization: Elgg 1.9 Themes

To create a theme for Elgg 1.9, you follow the standard plugin creation process as outlined in the Elgg developer guide : Two specific files control the landing page experience

To change styles, you can override elements/layout/columns.css by copying the core file to your plugin's views/default/elements/layout/ directory. Elgg 1.9 Themes

This default theme introduced a fresher color palette and a layout designed to work across desktop and mobile screens. Step-by-Step: Creating a Basic Theme Plugin

Use the vars:compiler hook in your plugin's PHP configuration to override global CSS variables like colors and widths.