... and until you've done that, don't put your name on the drawing! For, what have you done sofar? Really nothing but changed some colors, right? Once you change it substantially enough - then you may add your signature too!
As far as I know, if you change the drawing in *any* fashion from the original creator's version, then your name goes on it, if for no other reason than to let the viewer know that it has been altered by your hand. To the best of my understanding, there is no minimum threshold for this, and there shouldn't be.
To put things in context, if I were to take one of your drawings, Bezo, repaint it in some garishly horrible paint scheme, and post it somewhere, wouldn't your rather your name *not* the be the last one that appears on the credits tag?
((Note, I'm not saying that the DD here is an example of that by any means))