How to modify lines of OTF spool

Hi all,

my requirement is to write in a sapscipt document a line with characters in white color (invisible when the document is printed but visible for a third software).

Since sapscript doesn't support colors, the only solution I think could work is to modify the OTF document once the spool is created.

Anyone knows about modifying OTFs specially if I want to change the color of characters???

One example of OTF line is this:

UL    +0000000000000

SW   00036

CT   FFFFFF00

ST   0220562CompanyID|Do
ST   0204162cumentID|DocType|DocumentStart|
ST   0027408ZipC
ST   0199162ode|Country|City|StreetAndNumbe
ST   0210362r|FirstName|LastName|Company|Ma
ST   0189058ilAddress

How can I know what numbers to change in order to manipulate the characters format?

Thanks,

ILIE