WYSIWYG Editor should show same font attributes as on Theme

Well, i already tried to research this topic, but somehow always ended up with WYSIWYG Editor plugins that don’t do what i want.

There was also
https://wiki.moxiecode.com/index.php/TinyMCE:Plugins
but that site has me lost, can’t find any download links……

What do i really really want??
well, a million dollars and a nice gal – uhps, wrong forum, lets get serious again, i want this:
Lets say i use
Tahoma, size 16px, color #00000
in my Theme’s CSS file for the general stadard posts text.

Now i simply would like that my WP Admin WYSIWYG Editor text panel would display the exact same font size and color while i type in new contents, that’s all!

Maybe a Plugin like
WP Super Edit
could actually give me the option to at least select these font attributes before or while i type, but the description sounds a bit unclear and i am also not sure if this plugin goes and messes up the standard WP WYSIWYG settings, something i would not want of course. It also looks a bit bloated and i ask myself also what happens if someones uses this Plugin and sets the font attributes to say “Arial, 24px, #55f5f5 – yet the Themse CSS is set on Tahoma, size 16px, color #00000, would that just simply not work i guess??

So, there must be somewhere either a CSS or PHP file within the bundle of WordPress files (i never dared to even look into so far) in which i could simply change the CSS for the standard display in the WYSIWYG Editor’s text field???

If yes, could anyone point the file name / folder / lines to change out for me??