The bug

For Warped and Crimson Stems and Hyphae the respective stripped variants look the same in gameplay, but have different colors on the map.

Expected:
As the textures of stripped stems and stripped hyphae look the same, I would expect them to have the same color on the map

How to reproduce

Go to an open, flat space. The following commands fill a small area to the south-east at the level beneath the player feet with warped/crimson hyphae/stems. Observe colors on a map. Compare to in world textures and colors.

/fill ~ ~-1 ~ ~4 ~-1 ~4 minecraft:stripped_warped_hyphae
/fill ~5 ~-1 ~ ~9 ~-1 ~4 minecraft:stripped_warped_stem[axis=z]
/fill ~ ~-1 ~6 ~4 ~-1 ~11 minecraft:stripped_crimson_hyphae
/fill ~5 ~-1 ~6 ~9 ~-1 ~11 minecraft:stripped_crimson_stem[axis=z]

Code analysis

Code analysis by Avoma can be found in this comment.

Related to

MC-175228 Many stripped wood and log blocks have incorrect/inconsistent map colors