As far as the arrow graphics themselves, sometimes the arrows are solid lines and sometimes they are merely outlines of arrows. Conventionally, the colors of the arrows are red, blue, or black. Red and blue current arrows represent warm and cool currents, respectively. Display techniques depend largely on the scale of your map. A map of the world would show the major ocean currents and current name labels. A large‑scale map showing just one beach along a shoreline, though, or one bay, could have a great number of arrows to show every little current that exists. Current velocity can be shown with symbol levels by using longer arrows (or whatever symbol you are using) for the high‑velocity currents and shorter arrows for the low‑velocity currents. (See Figures 6.50 through 6.53 for examples how to depict this feature in certain situations.)