It depends on whether you saved your images as camera generated JPEGs or if you saved the raw image data. If you've got the raw image file, you can still make color images from those shots. If all you have is a camera generated JPEG, the color information has been irretrievably discarded.
A camera generated jpeg uses the raw data collected by the image sensor and creates a viewable image with it based on the instructions/settings active in the camera at the time. All of the unused information from the raw data is discarded and not recorded to the memory card.
When you save the raw file, pretty much all of the raw data collected by the sensor is preserved. The instructions/settings active in the camera at the time are used to generate a jpeg preview image that is included in the raw file. This is what you see on the camera's rear LCD when you review the image. It is also what you often see when you initially open a raw image file on your computer. The difference is that the preview image is just one of a near countless number of possible interpretations of the raw data that are all equally as valid. All of the data needed to produce a totally different interpretation (such as color instead of B&W is still contained in the raw file.
For more, please see:
Can I save color images while reviewing them in B&W with an EOS camera?
Why do my photos look different in Photoshop/Lightroom vs Canon EOS utility/in camera?
Is the Preview file always the photo taken by the camera?
Why are my RAW images already in colour if debayering is not done yet?
Assuming no editing, what's the difference between in-camera jpegs and lightroom jpegs? which includes the below in one of the answers:
One quite easily discernible example: Shoot in B&W in-camera and save the raw data. Then open those raw "images" in Lightroom using LR's default settings. When you open the raw files LR will render a color image from the raw image data. Note that in the Preview section of LR, the attached JPEG preview may be used which will show the B&W preview JPEG, but if you use the Develop module of LR with a generic profile selected it will render the image in color using the raw image data collected by the sensor.
If you open a raw image file that was shot when the camera was set to B&W and the first thing you see is still a B&W image, it means the application that opened the raw file either used the camera generated JPEG preview, or it followed the in-camera instructions/settings recorded when the image was taken. All you need to do to process the image in color is to change the setting in your application from B&W to one of the color processing settings.