/* https://grabient.com/_gItgsmgAQgHKgtMgAWgGcgBlgTYgKOgIBgHl?style=linearGradient&steps=7&angle=225 */

background: linear-gradient(225deg, #4c0000 0.000%, #7a0302 16.667%, #ac1609 33.333%, #d83009 50.000%, #f75202 66.667%, #ff7c00 83.333%, #f9ac03 100.000%);

<svg xmlns="http://www.w3.org/2000/svg" width="800" height="400" viewBox="0 0 800 400" preserveAspectRatio="none">
            <!-- https://grabient.com/_gItgsmgAQgHKgtMgAWgGcgBlgTYgKOgIBgHl?style=linearGradient&steps=7&angle=225 -->
            <defs>
              <linearGradient id="gradient" x1="0.854" y1="0.146" x2="0.146" y2="0.854">
        <stop offset="0.000" stop-color="#4c0000" /><stop offset="0.167" stop-color="#7a0302" /><stop offset="0.333" stop-color="#ac1609" /><stop offset="0.500" stop-color="#d83009" /><stop offset="0.667" stop-color="#f75202" /><stop offset="0.833" stop-color="#ff7c00" /><stop offset="1.000" stop-color="#f9ac03" />
              </linearGradient>
            </defs>
            <rect x="0" y="0" width="800" height="400" fill="url(#gradient)" />
          </svg>

["#4c0000", "#7a0302", "#ac1609", "#d83009", "#f75202", "#ff7c00", "#f9ac03"]

// https://grabient.com/_gItgsmgAQgHKgtMgAWgGcgBlgTYgKOgIBgHl?style=linearGradient&steps=7&angle=225
// cosine gradient palette — https://iquilezles.org/articles/palettes/
const float STEPS = 7.0;
const float ANGLE = 225.0;

vec3 palette(float t) {
    vec3 a = vec3(0.557, 2.854, 0.016);
    vec3 b = vec3(0.458, 2.892, 0.022);
    vec3 c = vec3(0.412, 0.101, 1.240);
    vec3 d = vec3(0.654, 0.513, 0.485);
    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);
}

[
  [0.557, 2.854, 0.016],
  [0.458, 2.892, 0.022],
  [0.412, 0.101, 1.240],
  [0.654, 0.513, 0.485]
]

Gradient palette editor — #4c0000 to #f9ac03