What does the cart color at the top of my shop mean?

Short answer: It is the shop's opening state. Red: it does not accept orders. Amber: a validation by DAGOBA is still pending, and you can click to request it. Green: it is open and processing orders.

In the "Activation + Shop address" section, next to the address. The icon carries no text: on hover, a tooltip gives the exact state, and in the red case, the precise reason.

Red cart — the shop does not accept orders. The tooltip reads "The shop is closed (payment methods disabled) because…" followed by the cause: an address still containing the word demo, or a logo in use whose print quality is insufficient. It also gives the move to make.

Amber cart — DAGOBA still has to validate the shop. The tooltip reads "DAGOBA must validate the shop, click to request validation". This is the only state where the icon is clickable: one click records your request.

Green cart — the shop is open. The tooltip reads "Shop opened and processing orders". The payment methods are active.