If you really want this functionality it should be added by a plugin, any chance of ripping out the previously removed bukkit commands as plugins thinkofdeath for compatibility?
Ugh formatting issues :/
/tellraw @a {color:purple,text:"Hello vanilla!"}
At this point its better to follow vanilla commands so I wont be changing this.
I have however re-enabled selectors for players/console so you can do
/tellraw @a
To get the same result + more features
Was just about to create a ticket for this. 
I like the purple too.
Bammerbom
I think we can wait for Thinkofdeath to see this and he can leave his input on this. I'm not too awfully familiar with the bug reporting process, so I'm not sure if refiling is necessary or if it's fine until he reviews it.
@Justin W. Flory
I liked the purple color. Maybe ask a dev to change this back.
Edit: Help how do I tag someone?
Bammerbom
Ah, so this was a recent change. Might it be worth a discussion to either revert the /say back to the purple color or perhaps make this customizable to the server owner in spigot.yml?
Every command overwritten by bukkit changed to the default minecraft ones. The one of minecraft has no purple color.
So it is intended behaviour, but I liked the purple color.