Yes, a color image can be stored in black and white. When this is done, each pixel's red, green, and blue (RGB) values are combined into a single grayscale value. This can be done using image editing software such as Adobe Photoshop or Lightroom. The process of converting a color image to black and white is often referred to as desaturation.
In Photoshop, you can convert a color image to black and white by selecting Image > Adjustments > Black & White. This will open the Black & White adjustment panel, where you can adjust the conversion settings to your liking. You can also use the Gradient Map adjustment to create a black and white image with a specific tone or contrast.
Alternatively, you can use online tools to convert color images to black and white. These tools typically allow you to upload your color image, preview the black and white conversion, and then download the resulting image.
It's worth noting that when you convert a color image to black and white, the resulting image will only have shades of gray, as the color information is discarded. Therefore, it's important to consider the tonal range and contrast of the image when converting it to black and white.