#00618A

CSS

:root {
  --blue-velvet: #00618a;
  --blue-velvet-rgb: 0 97 138;
  --blue-velvet-oklch: oklch(0.466 0.1 236.1);
}

.element {
  color: var(--blue-velvet);
  background-color: hsl(198 100% 27%);
  border-color: oklch(0.466 0.1 236.1);
}

Tailwind CSS v4

@theme {
  --color-blue-velvet: #00618a;
  --color-blue-velvet-50: #dcfaff;
  --color-blue-velvet-100: #caeeff;
  --color-blue-velvet-200: #addbfb;
  --color-blue-velvet-300: #86bfe5;
  --color-blue-velvet-400: #60a8d2;
  --color-blue-velvet-500: #3690c0;
  --color-blue-velvet-600: #307aa2;
  --color-blue-velvet-700: #266182;
  --color-blue-velvet-800: #184860;
  --color-blue-velvet-900: #0f3243;
  --color-blue-velvet-950: #021d2b;
}

SCSS

$blue-velvet: #00618a;
$blue-velvet-rgb: 0, 97, 138;
$blue-velvet-light: mix(#fff, $blue-velvet, 20%);
$blue-velvet-dark: mix(#000, $blue-velvet, 20%);

.element {
  color: $blue-velvet;
  box-shadow: 0 0 0 2px rgba($blue-velvet, 0.35);
}