In an idealized situation, where the threads contained all the primary colors in equal amounts, and were not obscured by dirt and other residues, the lint would appear to be white, not gray.
If you haven't seen these nymphs before on the site, they're actually jet black: the white coating is lint and dirt that they glue to themselves with spittle to form camouflage.
可能你从没有见过这样的若虫，他们实际上是深黑色的：白色的外衣是绒毛和它们用唾液粘上作为伪装的灰尘。
3
A man placed a spool of white thread in an inside suit coat pocket and threaded it through his coat lapel to make it look like lint.