I am painting something for my grandmother as a Christmas gift, but I don't know what colors to use. It will be the twin towers on a metallic pastel rainbow background. I was thinking either red, blue, black, or a mixture of the three. But I can't decide. Help me please <3

What I did with the background is painted it with a metallic white acrylic, then painted over it with water colors in a diagonal rainbow to cover it. I know most wouldn't do that, but it adds a really pretty pastel hue to the canvas and then makes the subject matter pop. I will be finishing the painting in acrylic. smile

Thanks~