Wii only shows blue, yellow and black on my HD TV

The Wii Guitar Hero guitar is not compatible with Wii Rock Band.
Source: http://gamesweasel.com/blog/matts-blog/using-the-wii-guitar-hero-controller-with-rock-band/
Sorry for your luck, but that site does list alternatives which you can buy.

where? the Wiimote? maybe the Battery is low or something, maybe you could bring down a little details, I'm just using the Guitar Hero Guitar on the Rock Band 2, Here It's very slowly updated with cool games... Can't even find the Guitar Hero 5 in the game stores...

have you tried blowing the outlet to the wiimote and guitar then pluging it in

Unfortunately, the guitar that comes with the Guitar Hero does not work with Rock Band or Rock Band 2. Rock Band, as you mentioned, recognizes the Wiimote as the controller for the microphone.

Unfortunately, you will have to get a guitar that is specifically designed for Rock Band.

I know this isn't the answer that is popular, but if you vote for my solution, please vote at least "Thanks for Trying".

Thanks for using Fixya!

check this link for a complete matrix of which instruments work with which games on which consoles http://www.joystiq.com/Instrument-Compatibility-Matrix/

guitar hero controllers were not meant to be compatible with rock band on wii for some dumb reason, the only rock band compatible with those guitars is rock band 2, my world tour guitar doesn't even register on rb1

Rock Band and Guitar Hero instruments are NOT compatible on the Wii. They are compatible on the 360, the PS3, and the RB drums for PS2. Activision went their own way with the Wii and made life difficult for all of the aspiring musicians on the Wii. Sorry.

Rock Band and Guitar Hero instruments are NOT compatible on the Wii. They are compatible on the 360, the PS3, and the RB drums for PS2. Activision went their own way with the Wii and made life difficult for all of the aspiring musicians on the Wii. Sorry.

guitar hero and rockband insturments will not work for the opposite game. however, if you have the option to return the guitar hero guitar, there is a guitar that is universal

This cant be done for the wii sadly because the guitars can not be switched, so you would have to use 2rock band guitars for rock band and 2Gh controllers for Gh.