There is rarely one right answer. Here are several categories of pairing options, each with a reason it may work.
Cobalt Green
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Sea Green
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Jade
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Verdigris
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Teal
Enough lightness contrast to read as two distinct colours without feeling harsh.
Pewter
Enough lightness contrast to read as two distinct colours without feeling harsh.
Sage Green
Enough lightness contrast to read as two distinct colours without feeling harsh.
Emerald Green
Enough lightness contrast to read as two distinct colours without feeling harsh.
Grey
A low-chroma neutral lets the original colour stay the visual focus.
Ash Grey
A low-chroma neutral lets the original colour stay the visual focus.
Silver
A low-chroma neutral lets the original colour stay the visual focus.
Taupe Grey
A low-chroma neutral lets the original colour stay the visual focus.
Ruby
A saturated accent from a different hue family for a deliberate pop of contrast.
Cerise
A saturated accent from a different hue family for a deliberate pop of contrast.
Crimson
A saturated accent from a different hue family for a deliberate pop of contrast.
Cherry Red
A saturated accent from a different hue family for a deliberate pop of contrast.