The bug
Despite their colors being very different, glow lichen use the same color as vines on maps. If this is unintentional, then it is most likely due to reusing code from vines for glow lichens (or the other way around).
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Linked issues
relates to 11
MC-148982
Map color for wheat is incorrect
Resolved
MC-175228
Many stripped wood and log blocks have incorrect/inconsistent map colors
Open
MC-190064
Pistons are gray on maps in positions they should not
Open
MC-201332
Normal shulker box and purple shulker box have wrong color on maps
Open
MC-201333
Dark prismarine, stairs or slab and prismarine, stairs or slab have wrong color on maps
Open
6 more links
Can confirm.