There is rarely one right answer. Here are several categories of pairing options, each with a reason it may work.
Storm Grey
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Slate Grey
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Egyptian Blue
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Denim Blue
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Slate Blue
Enough lightness contrast to read as two distinct colours without feeling harsh.
Royal Blue
Enough lightness contrast to read as two distinct colours without feeling harsh.
Petrol Blue
Enough lightness contrast to read as two distinct colours without feeling harsh.
Dark Slate Grey
Enough lightness contrast to read as two distinct colours without feeling harsh.
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.
Lime
A saturated accent from a different hue family for a deliberate pop of contrast.
Gold
A saturated accent from a different hue family for a deliberate pop of contrast.
White
Meets WCAG AA contrast (5.8:1) for normal text if used as text/background.
Ivory
Meets WCAG AA contrast (5.8:1) for normal text if used as text/background.
Mint Cream
Meets WCAG AA contrast (5.7:1) for normal text if used as text/background.
Azure
Meets WCAG AA contrast (5.7:1) for normal text if used as text/background.