how to change the default desktop background bliss for all users of a local computer for instance for a white color

Some other articles that might be useful:

permanent desktop background:
http://techrepublic.com.com/5208-6230-0.html?forumID=101&threadID=213060&messageID=2182977

remotely changing wallpaper with a script:
https://www.experts-exchange.com/questions/23755088/remotely-changing-wallpaper-with-a-script.html

The simplest way to do this would be to login to the machine as administrator, rename "bliss.jpg" to "blissOLD.jpg" and then create a new "white" image and save it as "bliss.jpg" in the same folder.    The users, of course, could still change their background image if they have the proper permissions.  It is a sleight really, but to accomplish this goal quickly, it would work.

Now, if you only want to change the background color, then we are talking about modifying the "theme":

Customizing XP luna theme via group policy?:
http://techrepublic.com.com/5208-6230-0.html?forumID=101&threadID=234723&messageID=2306392

More on themes:

http://books.google.com.mx/books?id=UsrjAAHJDE4C&pg=PT108&lpg=PT108&dq=%22windows+xp%22+AND+%22save+a+theme%22&source=web&ots=4aUeL6zarf&sig=wBuGpsRaGwLujGuhhBOwIyxfTYk&hl=en&sa=X&oi=book_result&resnum=8&ct=result#PPT107,M1

You can modify the theme the way you like it, then save it, pick the theme files and apply it to the other computers with group policy.

Here is another article about changing and avoid users from changing themes:

Apply Theme in Windows XP?:
http://forum.bigfix.com/viewtopic.php?id=209

pablovr:

thanks a lot for you feedback. very nice effort.
Look your first answer i think is near the solution:

Start - > Run -> type "gpedit.msc"

Then:
go to the "User configuration" then to "Administrative Template" then "desktop" then "active desktop" and enabled the "active desktop wallpaper".

After that:

But instead of a bmp i need the desktop background to (None) and white color for all users.