How can I add an overlay on image background ?

The community member Romaric wants to add an overlay with an RGBA color (rgba(0, 0, 0, 0.3)) on an image background to improve the contrast of a message, similar to what Webflow does. Romaric tried adding a gradient but it didn't work. Other community members explain that in CSS, background colors cannot be added directly over images, so Webflow and the community members will convert the single color to a gradient (like linear-gradient(#333, #333)) to achieve the desired effect. The community members confirm that this solution works and provide a link to a related UI project.