Streamlines can be colored using any scalar field function. Expand the Scenes node and select and expand a scene which contains a streamline displayer. Expand the Displayers node and the streamline displayer node, and select the Scalar Field node.
By default the function is not set. To set the scalar field function choose from the drop-down list next to the Function property in the Properties window.
The scalar values will appear on the streamlines in the display.
The units and range of the scalar field function can be changed in exactly the same way as in the Scalar Displayer.