There is rarely one right answer. Here are several categories of pairing options, each with a reason it may work.
Gunmetal
Enough lightness contrast to read as two distinct colours without feeling harsh.
Graphite
Enough lightness contrast to read as two distinct colours without feeling harsh.
Taupe
Enough lightness contrast to read as two distinct colours without feeling harsh.
Prussian Blue
Enough lightness contrast to read as two distinct colours without feeling harsh.
Tomato
Strong lightness contrast and saturation for a bold, graphic pairing.
Vivid Coral
Strong lightness contrast and saturation for a bold, graphic pairing.
Saffron
Strong lightness contrast and saturation for a bold, graphic pairing.
Royal Blue
Strong lightness contrast and saturation for a bold, graphic pairing.
Yellow
A saturated accent from a different hue family for a deliberate pop of contrast.
Chartreuse
A saturated accent from a different hue family for a deliberate pop of contrast.
Cyan
A saturated accent from a different hue family for a deliberate pop of contrast.
Spring Green
A saturated accent from a different hue family for a deliberate pop of contrast.
White
Meets WCAG AA contrast (21.0:1) for normal text if used as text/background.
Ivory
Meets WCAG AA contrast (20.8:1) for normal text if used as text/background.
Mint Cream
Meets WCAG AA contrast (20.6:1) for normal text if used as text/background.
Azure
Meets WCAG AA contrast (20.5:1) for normal text if used as text/background.