When you Save Blender, the Images should be Saved as well. When you just close (exit?) Blender, the file doesn't get Saved and the Reference Images are lost as well...
Is that what you are experiencing?
2 loves
Omar Domenech
replied
Solution
You may have moved files from folders on your computer or rename a file. When you do that the link gets broken and Blender doesn't know where to source the image from and turns it with that pink color, signifying that it can't find it. It's just a matter of uploading the image into Blender again or pointing out the new path on your computer so it refreshes it and loads it up again.