Alright.
First off, I used this like a few months ago when I still played.
This thing allows you to change achievement names and it's really simple, just don't abuse it or it might get taken away.
Step 1.
Go to Wowhead: WoW Database Extraordinaire
Go to their Achievements section, click on one.
Step 2.
Click on the red "Link" button.
and copy pasta into chat.
You should see
/script DEFAULT_CHAT_FRAME:AddMessage("Shift-click this to place a link into a chat message: \124cffffff00\124Hachievement:277:"..UnitGUID("player")..":0:0:0:0:0:0:0:0\124h['Tis the Season]\124h\124r");
Step 3.
You see the [Tis the season] near the end?
Basically change that to whatever text you. You can use arrows keys to move to that.
And then done, it should come out when you post it instead of Tis the season, it should be like [I'm Ftw], but when you right click it it will still give you the same achievement description.
Alright, heres how to change achievement COLORS.
Step one,
Pick a color from Web Color Chart - Hexadecimal - by VisiBone
Step 2.
Take an achievement, say
/script DEFAULT_CHAT_FRAME:AddMessage("Shift-click this to place a link into a chat message: \124cffffff00\124Hachievement:277:"..UnitGUID("pla yer")..":0:0:0:0:0:0:0:0\124h['Tis the Season]\124h\124r");
Now change the bolded stuff, the last 6 characters.
and change that to what code your color is.
Your final result should be
/script DEFAULT_CHAT_FRAME:AddMessage("Shift-click this to place a link into a chat message: \124cff999933\124Hachievement:277:"..UnitGUID("pla yer")..":0:0:0:0:0:0:0:0\124h['Tis the Season]\124h\124r");
The bolded part was what was changed.