I'm just watching "Silent Enemy" right now. It looks like CBS did some digital altering of the color compared to the DVD picture just to make it look better, but it's nothing like color change that was done for TOS or TNG---it doesn't give it that "WOW" feeling (and for the shot of the ship at warp, just after Hoshi and Reed share dinner together it looked like for a minute it went to black and white).
But if you look at 27:23 on both the Blu-Ray and DVD, you can see that the shot is reframed for the Blu-Ray for some reason. Aside from shifting the picture over to center it, it really doesn't add to the image (infact it displays more of the graphic on the back wall, that fades into black because of how the lighting was done).
And the CGI creatures in this episode just do not stand up well, they look like some horrible 1950's Sci-Fi alien made out of clay, or something that should be in a Nintendo 64 game.