You have likely heard people talk about the Golden Hour with photography - the time in the late afternoon when the sun is low in the sky and the light is warm.
Well there is another concept - Blue Hour which is the time just after sunset, the sun is below the horizon, the night sky is starting to kick in and you get an unusual mix of a blue night sky and the thin strip of ornage of gold from the sun.
Recently I was at Palm Cove, just north of Cairns in Queensland Australia and we were walking along the foreshore just after sunset and I took this series of photos with the Palm trees that give Palm cove it's name silhouetted against the Blue Hour sky.
All photos were taken with my trusty Fujifilm X-T3 combined with the less common 16-80mm X-mount lens. This is a lens which not too many people use but I think is a great zoom lens to take with you when you are travelling, it's still relatively small, but the 16mm to 80mm (basically 24mm to 120mm full frame equivalent will cover 90% of my shooting requirements.
In most instance I do fast shutter speed - something like 1/250 of a second or maybe 1/125mm and stop it right down to F18 or so to turn the shadows truly black and give a depeth to the colour of the sky.