The ads on the bus go round and round, round and round, blah blah blah.
I grabbed an image of one of the new buses and coloured it blue by painting the colours roughly onto a new layer and setting the layer blend mode to colour. I then tidied the layer up using a mask.:
After this I started layering type and graphics that I created onto the bus. The gradient on the ad space on the bus is just a hard brushed dark blue with a Gaussian blur applied to it which I then masked to restrict it to the ad board space. The bubble effect over the gradient was created by selecting a hard brush and changing brush settings to scatter with size,opacity and flow jitter.