There is rarely one right answer. Here are several categories of pairing options, each with a reason it may work.
Royal Blue
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Amethyst
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Medium Purple
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Blue Violet
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Payne's Grey
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.
Persian Blue
Enough lightness contrast to read as two distinct colours without feeling harsh.
Denim Blue
Enough lightness contrast to read as two distinct colours without feeling harsh.
Taupe Grey
A low-chroma neutral lets the original colour stay the visual focus.
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.
Yellow-Green
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.
White
Meets WCAG AA contrast (5.3:1) for normal text if used as text/background.
Ivory
Meets WCAG AA contrast (5.3:1) for normal text if used as text/background.
Mint Cream
Meets WCAG AA contrast (5.2:1) for normal text if used as text/background.
Azure
Meets WCAG AA contrast (5.2:1) for normal text if used as text/background.