To create a shaded featured post at the top of an archive page, use the Visibility setting (in the Publish box on the right of the Edit screen) to mark the post as sticky. In Grid Loop archives, the sticky post will appear above both Features and Teasers.
On your News / blog page, all sticky posts will appear at the top of the first page. On all other archives, only the single most recent sticky post will appear.
Sticky posts’ featured images are Medium-sized and aligned to the right, regardless of the image size chosen in the Theme Settings’ Content Archives section or the Grid Loop settings. See the documentation on Featured Images for the code required to change this behavior.
To change the sticky post styles, copy the .sticky and .stickies styles into your custom CSS and adjust as needed:
.entry, .entry.sticky,
.entry.sticky.has-post-thumbnail,
.after-entry.widget-area { padding: 16px 24px; }
// Pool (default) color scheme
.content .stickies .entry.sticky,
.blog .entry.sticky { background: #e5f0f6; color: #003262; }