Using Lightroom for Black and White
Adobe Photoshop Lightroom has a great many tools editing your photos, but one of my favorites is the black and white conversion process. To use it, I first make a virtual copy of my color image (this doesn't work with an image you've shot in black and white, and doing that negates all the advantages of digital capture.) In the Develop module, first make basic tonal adjustments, then click the "Black & White" tab under the "Basic" adjustments.
But here the fun begins. Scroll down to the HSL/Color/B&W tab and you'll find eight sliders for the three primary channels and various combinations, e.g., Orange, which is a combination of Red and Yellow channels. These allow you to apply black and white filters after the fact in endless combinations. You can play with them to your heart's content, since Lightroom adjustments are non-destructive.
For this shot of St-Chapelle in Paris, I boosted the Orange and Yellow sliders and reduced the Aqua, Blue, and Purple sliders. After making these changes, I returned to the tonal adjustments to make certain my changes weren't blowing anything out or blocking up shadows.
Because this is Lightroom, I can go back at any time and change the mix, add a curve, even introduce split toning, and my original color image is untouched.