I'm sure it's been asked, but...

Could be bad cables.

You say you're using "component"...

Have you tried composite or any other method, just to see what else it's getting?

Since you say it's only the digital channels, I wonder if something's wrong with the outputs on the cable box, too.

Give us more details on how EVERYTHING is connected.

Box tto TiVo, box to TV, TiVo to TV, etc. (Any other units involved as well.)

TiVo to TV should use "composite" or s-video connection.

From the HD cable box use the HDMI or "component" connections to the TV. Use the composite from HD box to TiVo if you're recording from it (in SD of course).

That would depend on his "TiVo" model. My SD-H400 has component video outputs that I'm using with no problems.

I'm curious about the "Only applies to channels above 99" statement. Are you saying that channels below 99 output color fine from your TiVo with your hookup but as soon as you tune to one above 99 it's black and white?