I don't have a photo of a gray hairstreak larva that is ready to form a chrysalis; but lycaenid larvae tend to change color when they are finished eating and are ready seek a place to pupate and form a chrysalis. 

Examples of this can be seen in this section of the website. One practical option is to place them in facial tissue and fold into three equal rectangular sections.  Then, rotate 90 degrees and fold into thirds again.  (If that sounds complicated, watch the first minute of this video.)