I’m working on the Loremaster achievement with a level 70 toon and it’s quite hard to see the trivial quest markers on the map or when flying over. I’d love to find an addon that would allow me to change the color of the trivial quest marker (!) so something that stands out.
Has anyone seen anything like this?
Sexymap?, is my first guess without looking more into it atm
Unfortunately you can’t modify things on the map, you can only draw on top of them, and I’m pretty sure you need to know the coords ahead of time.
This might help:
https://www.curseforge.com/wow/addons/handynotes-loremaster
I was afraid this was the case. I’ll look at the handy notes solution. I also found an addon that will keep track of all the questlines for the various zones. It makes it easier to know where you are in the quest lines.
But those pesky trivial ! markers are almost impossible to see unless you stop and study the map 
You used to be able to replace the texture file with all of the map blip textures to change the icons. Did they remove that? (It was always a pain to do and it tended to break horribly with most patches, so I gave up trying some time in Legion.)
No idea. I’m mostly, and possibly incorrectly, remembering Gello and/or Fizzle saying changing stuff on the minimap wasn’t possible because it’s considered a single layer.