There is rarely one right answer. Here are several categories of pairing options, each with a reason it may work.
Lavender
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Mauve
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Thistle
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Lavender Blush
Similar lightness for a subtle, tone-on-tone pairing with minimal contrast.
Lilac
Enough lightness contrast to read as two distinct colours without feeling harsh.
Dusty Lavender
Enough lightness contrast to read as two distinct colours without feeling harsh.
Plum
Enough lightness contrast to read as two distinct colours without feeling harsh.
Silver
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.
Lavender
A low-chroma neutral lets the original colour stay the visual focus.
Lavender Blush
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.
White
A low-chroma neutral lets the original colour stay the visual focus.
Tyrian Purple
A saturated accent from a different hue family for a deliberate pop of contrast.
Chocolate Brown
A saturated accent from a different hue family for a deliberate pop of contrast.
Maroon
A saturated accent from a different hue family for a deliberate pop of contrast.
Indigo
A saturated accent from a different hue family for a deliberate pop of contrast.
Black
Meets WCAG AA contrast (13.6:1) for normal text if used as text/background.
Navy Blue
Meets WCAG AA contrast (10.4:1) for normal text if used as text/background.
Midnight Blue
Meets WCAG AA contrast (9.7:1) for normal text if used as text/background.
Prussian Blue
Meets WCAG AA contrast (8.7:1) for normal text if used as text/background.