Faint Brown -- how does it affect price?

[diamondnab]

Hello! I recently came across a 1.85 K color round diamond that is Excellent cut (GIA), but noticed it had Faint Brown on the report. I read that brown in the body will negatively affect the price, but does anyone know by how much? For instance how much lower should I pay than a comparable 1.85 K color Excellent cut with no Faint Brown? Estimated dollar amounts or percentages (20% lower) would be great! I just want to make sure I'm not overpaying. Thanks in advance for your help!