It’s in the po st spot colour
There is a quick and easy technique that can be used in post-production to isolate your subject and that is also a graphic use of colour. It may be a bit of a cliché, but is still very effective. Simply keep spot colour on the main subject while desaturating the rest of the scene. You have probably seen this technique used with a bright red double-decker bus against a black-and-white background, or in wedding photos to highlight the colours in a bouquet.
First make a quick selection of your subject in Photoshop using the lasso tool (the magnetic lasso can make things easier if your subject is something with a detailed outline, such as a tree). Hit Shift + Cmd/Ctrl + I to invert the selection, then choose Image>Adjustments>Hue/ Saturation and move the Saturation slider all the way to the left to remove the colour from the background. For a subtler effect, try reducing the saturation in the background, but not removing the colour entirely.