Conduits have the wrong color on maps

The bug

Conduits use the color of prismarine on a map.

How to reproduce

1. Fill an area with conduits:

   /fill ~ ~ ~ ~10 ~ ~10 conduit

2. Obtain an empty map and fill it (by default, right click)
   The conduits, viewed from the map, appear to be close to the color of prismarine

Expected results

The conduits on the map would appear more brown than the color of prismarine because the block texture of a conduit is more brown than it is turquoise.