Drawing an issue has unclear lines

[mvl22]

When drawing an issue, the line is not very obvious:

Could we firstly apply some opacity to the map, so that it becomes more backgrounded. This can be set in L.TileLayer using e.g. opacity: 0.7.
https://leafletjs.com/reference-1.6.0.html#gridlayer-opacity

I think we could use red lines with a red+opacity fill instead, so that it stands out. Though the background map still has heavy red lines sometimes, so another colour might be needed. Either way, the current gray or light blue is not obvious.

Or, simply we should use the same as the issues list for consistency, which is clear: