Use hex notation for the default stroke colour

public/index.html

@@ -193,7 +193,7 @@
                 <b>Other colours</b>
               </div>
               <label id="colours">
-                <input id="other-colours" type="color" value="blue" />
+                <input id="other-colours" type="color" value="#0000ff" />
               </label>
             </div>
           </div>

src/canvas.js

@@ -16,7 +16,7 @@ const lineFn = line()
 
 const pathGroupElems = new Map()
 
-let strokeColour = "blue"
+let strokeColour = "#0000ff"
 let strokeRadius = 5
 
 const MAX_POINT_DISTANCE = 5