675 looks like the last three digits of the build sequence number to me (like "123675", or whatever). I have seen that before.
"White" would be a heads up to the painter so that he would know what color was coming up next.
Here are some of the threads I have accumulated that have to deal with graffiti, assembly line marking and grease pencil markings (if you are interested):
Factory Markings:
http://67-72chevytrucks.com/vboard/s...ighlight=Linda
Need Help Deciphering Factory Grease Marks:
http://67-72chevytrucks.com/vboard/s...ighlight=Linda
Show Us your Crayon Marks:
http://67-72chevytrucks.com/vboard/s...ighlight=Linda
Factory Grease Pencil Marks:
http://67-72chevytrucks.com/vboard/s...ighlight=Linda
Z Code Fremont Asssembly
http://67-72chevytrucks.com/vboard/s...light=graffiti
Found my Build Sheet:
http://67-72chevytrucks.com/vboard/s...light=graffiti
Numbers at top of firewall:
http://67-72chevytrucks.com/vboard/s...d.php?t=545345