How do I change an existing texture?

[Skemech]

So for fnaf in doom, I figured a clever way of showing what night your on, what in game time it is, and how much power is remaining is to use ur ammo counter in the player inventory ui. But I don't want it to say "BULL, SHELL, RCKT, and CELL". And if I copy and paste the texture in slade from DOOMII.wad into my wad in slade the image gets HEAVILY saturated and gray.

 

[Skemech]

I'm thinking like retitling BULL to be "Night". SHELL "Time". RCKT "Power"

[Skemech]

God damnit, I forgot hud message exsisted. thank you

[Skemech]

And of course, ChubZDoomer to the rescue. (This is just for anyone who has the same problem as I did)