There is rarely one right answer. Here are several categories of pairing options, each with a reason it may work.
Slate Blue
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Steel Blue
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.
Chambray
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Denim Blue
Enough lightness contrast to read as two distinct colours without feeling harsh.
Sapphire
Enough lightness contrast to read as two distinct colours without feeling harsh.
Payne's Grey
Enough lightness contrast to read as two distinct colours without feeling harsh.
Cobalt Blue
Enough lightness contrast to read as two distinct colours without feeling harsh.
Black
Strong lightness contrast and saturation for a bold, graphic pairing.
White
Strong lightness contrast and saturation for a bold, graphic pairing.
Mint Cream
Strong lightness contrast and saturation for a bold, graphic pairing.
Prussian Blue
Strong lightness contrast and saturation for a bold, graphic pairing.
Grey
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.
Graphite
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.
Yellow
A saturated accent from a different hue family for a deliberate pop of contrast.
Peridot
A saturated accent from a different hue family for a deliberate pop of contrast.
Citrine
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.
White
Meets WCAG AA contrast (4.8:1) for normal text if used as text/background.
Ivory
Meets WCAG AA contrast (4.8:1) for normal text if used as text/background.
Mint Cream
Meets WCAG AA contrast (4.7:1) for normal text if used as text/background.
Azure
Meets WCAG AA contrast (4.7:1) for normal text if used as text/background.