You can do this with an editing program.
I recommend using GIMP. It is available at gimp.org as a free download and comparable to Photoshop in many respects.
Using GIMP:
1. Open your image in GIMP. Open it twice so that you have two copies of the file open.
2. In one image window, choose Color > Desaturate. I recommend choosing the "Luminosity" option, but that is not required.
3. Use Control and A to select the entire image, then Control and C to copy the image.
4. Select the other image window, with the original (colored) image. Use Control and V to paste the black and white image over it.
5. Use Control and L to open your layers palette. Your black and white layer will appear as a floating image. Choose the button that looks like a white sheet of paper, in the lower left hand corner, to make it a new layer.
6. Right click the layer, and choose "Add Layer Mask". Leave the settings at their default and click "OK."
7. Choose the airbrush option and an appropriate brush. I would use the fuzzy circular brush in size 19. Change the Rate and Pressure sliders to their highest setting. Make the brush a size you feel is appropriate for the size of your object.
8. In the drop-down menu for Mode, choose "Color Erase." Click on the color swatch and change it to black.
9. Paint over the area of your object. It should become colored. Continue until you are satisfied.
10. Back in the layers palette that you opened before, right-click on the top layer and choose Merge Down.
11. Save your image.
If you would like to, send me your image and tell me what you want in color, and I can do this for you.
You can get a link for the image by uploading it at TinyPic.com or PhotoBucket.com. It will give you several links for the image; sending any one of them to me should be sufficient.