a) Do all the letters on a kosher haftorah scroll have to be in black ink?
b) What if the words and letters of one pasuk iare colored in gold — see illustration attached.
c) Can nonblack letters be colored over in black to make the klaf kosher?
- Yes all of the letters must be specifically in black ink.
- If part of the letters or pesukim are colored in gold it is also posul because the megillah then looks “menumar”- spotted, with different color ink.
- Regular letters can be colored over, but not the shem H-shem. In your instance one of the letters that are gold is shem H-shem, and it can not be corrected.
As a side point, it isn’t usual that a nach, which is usually a hiddur, should be written with such issues, as some of them as halachos that every sofer should know. I would check out if the sofer was religious or if he was Reform etc. or someone that didn’t care about halacha, which may be an even more serious problem. If he denies the authority of the halachic process, or if he didn’t specifically have in mind to write the shaimos with kavana, the sefer is posul.
Shulchan Aruch O:CH 32-3, Y:D 276-5, Taz Y:D 276-3, Shach Y:D 276-6,