Shades of grey on the image border in Grid View

[Laicamire]

Based on the image, was wondering what is the difference with the shades of grey on the borders of each photo. (Blue) is the image that I'm currently selecting but I'm unsure what does (pink) and (orange) mean. And why are all the (pinks) highlighted with the same shade of grey?

[Rob_Cullen]

THE FOUR SHADES OF GREY

1. MID-GREY :   Un-selected “NOT SELECTED”  image borders are MID-GREY.
   
   
2. LIGHT GREY :   WHEN MULTIPLE IMAGES ARE SELECTED,  I CALL THESE LIGHT GREY BORDERED FILES THE “SECONDARY SELECTED”. 

3. VERY LIGHT GREY:    The image selected that is the one “PRIMARY SELECTED”,  or the “MOST SELECTED” image among multiple selected images. 
   
   
4. DARK GREY:    Images with a VIRTUAL COPY or images belonging in a STACK,  all show as DARK GREY in library grid mode. (VCs stacked with original resume the MID-GREY shade as for 1. )

When multiple files are selected-

*Clicking on the IMAGE AREA in a thumbnail of one of the selected files upgrades this image to the “PRIMARY SELECTED”  image. (aka. “MOST SELECTED” image) and  the “Secondary” selections  (aka “Child” selections)  remain selected.

*Clicking on an image thumbnail GREY BORDER- deselects all other images, leaving one selected.