Why do my images appear to have lost color and saturation?

The problem is with the color space you selected. Anything displayed on the Web should be in sRGB color space, because that’s the only color space that web browsers understand. This means that any image using a color space other than sRGB will get converted to sRGB when the browser displays it. This will result in loss of color and saturation.

This means that even though it may be easier for you to edit work in adobeRGB or Prophoto color spaces, you should convert your images to sRGB before uploading them to the Web. You can do this in Photoshop by going to the Edit menu and selecting Convert to profile. In Lightroom, you can choose what color space you want when exporting your files.