Hey guys. I've also had this problem with my capture card as well, although I wasn't going through a VCR, just a lot of input boxes. It shows color on TV but B&W on PC. Well, I figured out how to make it work for me.
With my experience, the problem with a PC receiving black and white video is because of signal weakness. So, let me ask you this: How far away is your PC from your VCR? Or, even more important, how long is the coax cable that connects the two? The longer the cable, the weaker the signal will be, and when an average capture card receives a slightly weak signal, it makes up for it by showing the transmission in B&W. Really there are multiple problems, but also, multiple solutions.
So, here are some ways to fix this, in order of process of elimination of possible problems, easier-to-hardest.
1.) If you are using a very long coax cable to go from VCR to PC, try finding a shorter coax, maybe 5-feet, and see if that helps. If not...
2.) Does your console switch box have it's own power supply? If your console switch doesn't plug into the wall, chances are that is a big part of your problem. Console switches that are powered completely by video game hook-ups are TERRIBLE for video quality and strength. If it does plug into the wall, there is still a chance that it is weakening the signal, so try going directly from CONSOLE-to-VCR-to-PC. If that set up comes out black and white...
3.) Go on over to Radioshack, or some equivalent, and ask them if they have any cable signal amplifiers. There are simple little boxes, with a cable input and cable output. It plugs into the wall, and it's sole purpose is to amplify the signal of a coax output. You might want two of these if you are still going to use a long coax cable to go from your VCR to your TV. For one amplifier, use a short coax cable to go from VCR output into the amp. Then use the amp output to go to PC. If the cable from amp to PC is long, put another amplifier at the end of the cable close to the PC. If that still comes out black and white, keep the amps and...
4.) How old is your VCR? If it's a dinosaur, chances are that it doesn't amplify the signal as much as a more modern, digital VCR, so it's coax output is only strong enough to show good quality on an equally old TV. Try buying a newer, digital VCR that amplifies a strong coax output. Doubling your chances with new VCR + amplifiers should do that trick. But, if the new VCR falls through...
5.) Then try using one of those simple converter boxes, that is made for converting RCA input to coax output. MAKE SURE IT HAS IT'S OWN POWER SUPPLY, of course. Hook that directly from game console to PC. If THAT doesn't fix your problem, then...
6.) You probably have the same capture card as me, and it's a piece of complete shit. I'm assuming your capture card only has cable inputs, otherwise the last step would be directly console into PC, eliminating all of the common problematic variables in between the console and the PC.
Most commonly, if you get through half of these steps and the input is B&W, it's time to bite the bullet and get a new capture card, preferably one with RCA inputs. If you want to do really good-looking video game reviews, I would probably tell you to avoid coax all together. RCA is a MUCH MUCH MUCH better picture quality for viewing on computers in my experience. Plus, a lot of capture cards nowadays with a RCA input, the lag is almost zero. In fact, if your capture card currently has RCA inputs, just try that. The reason coax input has such a huge lag is because the card has to work harder to decode it into a video signal than it would have to work to decode RCA. If not, then get a new one. I'd say abut 90% of recent capture cards will give you just a millisecond or two of lag when using RCA, usually it's not noticeable at all., ESPECIALLY if it has a "game mode" feature, which is specifically made for playing video games using the capture card. Then you're golden.
Hope that helps!
EDIT: One temporary fix that I found by accident with my last card, was to sit there and watch the black and white feed, and leave it up on the screen. After about 30 minutes, after the capture card "warmed up" per se, it would suddenly switch to color! I have no idea why it did this, and I ended up replacing the card, but it worked consistently. Whenever I wanted to record something, I would just turn on the feed, then go do something else for about a half hour before I checked it again to find it in color.
