There is rarely one right answer. Here are several categories of pairing options, each with a reason it may work.
Orchid
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Violet
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Plum
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Lilac
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Mulberry
Enough lightness contrast to read as two distinct colours without feeling harsh.
Fuchsia
Enough lightness contrast to read as two distinct colours without feeling harsh.
Magenta
Enough lightness contrast to read as two distinct colours without feeling harsh.
Cerise
Enough lightness contrast to read as two distinct colours without feeling harsh.
Prussian Blue
Strong lightness contrast and saturation for a bold, graphic pairing.
Tyrian Purple
Strong lightness contrast and saturation for a bold, graphic pairing.
Cinnamon
Strong lightness contrast and saturation for a bold, graphic pairing.
Burgundy
Strong lightness contrast and saturation for a bold, graphic pairing.
Lime
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.
Chartreuse
A saturated accent from a different hue family for a deliberate pop of contrast.
Lime Green
A saturated accent from a different hue family for a deliberate pop of contrast.
Black
Meets WCAG AA contrast (7.9:1) for normal text if used as text/background.
Navy Blue
Meets WCAG AA contrast (6.0:1) for normal text if used as text/background.
Midnight Blue
Meets WCAG AA contrast (5.6:1) for normal text if used as text/background.
Prussian Blue
Meets WCAG AA contrast (5.1:1) for normal text if used as text/background.