When I draw a rectangle shape in Photoshop it has colour properties.
But when I draw a line it has no colour properties and just uses currently selected colour.
I want to change the colours of lines I have already drawn. How do I do this?
You have two basic options:
You can double click on the layer in Layer tab -> Layer style -> Color Overlay
You can change the color if you select your shape layer and up there you will see the shape tollbar. Fill option sets the color of the shape.
Hope it helps.