There is more to consider when creating such a scenario... an aspect you may not have considered yet would be validation. If you will be saving the input somewhere, do you plan to see if the user entered a name? Are you going to simply check for the prompt "Enter your name:" and dismiss that input?
The enter, leave, lostfocus etc events are fine to control what the textbox says and in what foreground color... but to make it really effective, especially if you're going to have many boxes like this, you should create your own control that handles the prompting and provides a validation method to the UI.
Just my .02 on the subject... as far as code, others have given you basic code to toggle text and forecolor... the rest is best left to existing tutorials on custom controls.
Best of luck!
Found one of the aritcles...