/* https://grabient.com/_gGEg8CeOcgEfg6Uh80gQJgBhgBjgHFgHegPG?style=linearGradient&steps=6&angle=225 */

background: linear-gradient(225deg, #1d2589 0.000%, #3c1caf 20.000%, #9421b6 40.000%, #a5359e 60.000%, #555666 80.000%, #1a8410 100.000%);

<svg xmlns="http://www.w3.org/2000/svg" width="800" height="400" viewBox="0 0 800 400" preserveAspectRatio="none">
            <!-- https://grabient.com/_gGEg8CeOcgEfg6Uh80gQJgBhgBjgHFgHegPG?style=linearGradient&steps=6&angle=225 -->
            <defs>
              <linearGradient id="gradient" x1="0.854" y1="0.146" x2="0.146" y2="0.854">
        <stop offset="0.000" stop-color="#1d2589" /><stop offset="0.200" stop-color="#3c1caf" /><stop offset="0.400" stop-color="#9421b6" /><stop offset="0.600" stop-color="#a5359e" /><stop offset="0.800" stop-color="#555666" /><stop offset="1.000" stop-color="#1a8410" />
              </linearGradient>
            </defs>
            <rect x="0" y="0" width="800" height="400" fill="url(#gradient)" />
          </svg>

["#1d2589", "#3c1caf", "#9421b6", "#a5359e", "#555666", "#1a8410"]

// https://grabient.com/_gGEg8CeOcgEfg6Uh80gQJgBhgBjgHFgHegPG?style=linearGradient&steps=6&angle=225
// cosine gradient palette — https://iquilezles.org/articles/palettes/
const float STEPS = 6.0;
const float ANGLE = 225.0;

vec3 palette(float t) {
    vec3 a = vec3(0.388, 3.842, -7.268);
    vec3 b = vec3(0.287, 3.732, 7.988);
    vec3 c = vec3(1.033, 0.097, 0.099);
    vec3 d = vec3(0.453, 0.478, 0.966);
    return a + b * cos(6.283185 * (c * t + d));
}

// N stops sampled from the palette, blended like the CSS gradient
vec3 stops(float t) {
    float n = STEPS - 1.0;
    float x = clamp(t, 0.0, 1.0) * n;
    return mix(palette(floor(x) / n), palette(min(floor(x) + 1.0, n) / n), fract(x));
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 p = fragCoord - 0.5 * iResolution.xy;
    // CSS angle: 0 = up, clockwise; span = CSS gradient-line length
    vec2 dir = vec2(sin(radians(ANGLE)), cos(radians(ANGLE)));
    float len = abs(iResolution.x * dir.x) + abs(iResolution.y * dir.y);
    float t = dot(p, dir) / len + 0.5;
    fragColor = vec4(stops(t), 1.0);
}

[
  [0.388, 3.842, -7.268],
  [0.287, 3.732, 7.988],
  [1.033, 0.097, 0.099],
  [0.453, 0.478, 0.966]
]

Gradient palette editor — #1d2589 to #1a8410