714.07 Amendments Not in Permanent Ink [R-11.2013]
37 CFR 1.52(a) requires "permanent dark ink or its equivalent" to be used on papers which will become part of the record. So-called "Easily Erasable" paper having a special coating so that erasures can be made more easily may not provide a "permanent" copy. However, because application papers are now maintained in an Image File Wrapper, the type of paper is unlikely to be an issue so long as the Office is able to scan and reproduce the papers that were filed.
See MPEP § 608.01 for more discussion on acceptable copies.