Why Does My Outdoor Banner Look Less Vibrant?

recently designed a banner for a temporary indoor exhibit, and I was asked to adapt the same design for a roadside banner outside the museum. The indoor banner looks vibrant and the text is very easy to read, but the outdoor banner doesn’t feel nearly as vibrant. The contrast that worked well indoors seems to be missing outside.

For example, there are feather overlays in the background that are clearly visible on the indoor banner, but they’re barely noticeable on the roadside version.

I’m wondering if anyone has advice or resources on how to adapt a design so it stays vibrant and readable in an outdoor environment.

For context, the roadside banner location doesn’t have any direct lighting and sits under several trees, so it’s often in shade.

Any tips or resources would be greatly appreciated. Thanks!