/* https://grabient.com/_fpXgAAgHYgmqgAAgIjgBjgBigGRgO4gAAgI5?style=linearGradient&steps=6&angle=315 */

background: linear-gradient(315deg, #e90000 0.000%, #fb0026 20.000%, #ff0066 40.000%, #ff00ab 60.000%, #f900e4 80.000%, #e500ff 100.000%);

<svg xmlns="http://www.w3.org/2000/svg" width="800" height="400" viewBox="0 0 800 400" preserveAspectRatio="none">
            <!-- https://grabient.com/_fpXgAAgHYgmqgAAgIjgBjgBigGRgO4gAAgI5?style=linearGradient&steps=6&angle=315 -->
            <defs>
              <linearGradient id="gradient" x1="0.854" y1="0.854" x2="0.146" y2="0.146">
        <stop offset="0.000" stop-color="#e90000" /><stop offset="0.200" stop-color="#fb0026" /><stop offset="0.400" stop-color="#ff0066" /><stop offset="0.600" stop-color="#ff00ab" /><stop offset="0.800" stop-color="#f900e4" /><stop offset="1.000" stop-color="#e500ff" />
              </linearGradient>
            </defs>
            <rect x="0" y="0" width="800" height="400" fill="url(#gradient)" />
          </svg>

["#e90000", "#fb0026", "#ff0066", "#ff00ab", "#f900e4", "#e500ff"]

// https://grabient.com/_fpXgAAgHYgmqgAAgIjgBjgBigGRgO4gAAgI5?style=linearGradient&steps=6&angle=315
// cosine gradient palette — https://iquilezles.org/articles/palettes/
const float STEPS = 6.0;
const float ANGLE = 315.0;

vec3 palette(float t) {
    vec3 a = vec3(-1.449, 0.000, 0.472);
    vec3 b = vec3(2.474, 0.000, 0.547);
    vec3 c = vec3(0.099, 0.098, 0.401);
    vec3 d = vec3(0.952, 0.000, 0.569);
    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);
}

[
  [-1.449, 0.000, 0.472],
  [2.474, 0.000, 0.547],
  [0.099, 0.098, 0.401],
  [0.952, 0.000, 0.569]
]

Gradient palette editor — #e90000 to #e500ff