Contour line overlay layer on other map types (e.g., satellite)

I sometimes set the transparency of the USGS Topo or the Gaia Contours Feet so that I can see that layer's contour lines and a satellite layer at the same time. But the 'no data' areas of the contour layers (white) still show up and just make the satellite image look milky and washed out. How about a vector layer that simply superimposes contour lines and is otherwise fully transparent, and the ability to select the contour line color. I don't know if this would have to be a .png raster image to support transparency or if you could do a vector render.