I couldn't imagine any interviewer who is going to choose not to hire you because your pre-private logbook entries are in blue ink.
Actually, i think "FIRST SOLO!!!!" is completely professional. Its one of the most important hurdles of your pilot career. I would smack your instructor if he didn't write something congratulatory in your logbook. Any interviewer with half a brain will remember what it was like on their first solo.
Don't you worry...it'll all be ok. There are guys out there (me) who had their logbooks stolen. Other guys do everything electronically. A little blue ink is what it is...its not like its pink highlighter.