There is rarely one right answer. Here are several categories of pairing options, each with a reason it may work.
Hunter Green
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Avocado
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Green
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Forest Green
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Moss Green
Enough lightness contrast to read as two distinct colours without feeling harsh.
Grey
Enough lightness contrast to read as two distinct colours without feeling harsh.
Storm Grey
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.
Grey
A low-chroma neutral lets the original colour stay the visual focus.
Graphite
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.
Ash Grey
A low-chroma neutral lets the original colour stay the visual focus.
Magenta
A saturated accent from a different hue family for a deliberate pop of contrast.
Blue
A saturated accent from a different hue family for a deliberate pop of contrast.
Ultramarine
A saturated accent from a different hue family for a deliberate pop of contrast.
Blue Violet
A saturated accent from a different hue family for a deliberate pop of contrast.
White
Meets WCAG AA contrast (5.9:1) for normal text if used as text/background.
Ivory
Meets WCAG AA contrast (5.9:1) for normal text if used as text/background.
Mint Cream
Meets WCAG AA contrast (5.8:1) for normal text if used as text/background.
Azure
Meets WCAG AA contrast (5.8:1) for normal text if used as text/background.