/* https://grabient.com/_gH0gGmgAAgZIgVMgAAgBlgBkgBlgKZgKugAA?style=linearGradient&steps=5&angle=135 */

background: linear-gradient(135deg, #000000 0.000%, #001800 25.000%, #274d00 50.000%, #688300 75.000%, #a9b900 100.000%);

<svg xmlns="http://www.w3.org/2000/svg" width="800" height="400" viewBox="0 0 800 400" preserveAspectRatio="none">
            <!-- https://grabient.com/_gH0gGmgAAgZIgVMgAAgBlgBkgBlgKZgKugAA?style=linearGradient&steps=5&angle=135 -->
            <defs>
              <linearGradient id="gradient" x1="0.146" y1="0.146" x2="0.854" y2="0.854">
        <stop offset="0.000" stop-color="#000000" /><stop offset="0.250" stop-color="#001800" /><stop offset="0.500" stop-color="#274d00" /><stop offset="0.750" stop-color="#688300" /><stop offset="1.000" stop-color="#a9b900" />
              </linearGradient>
            </defs>
            <rect x="0" y="0" width="800" height="400" fill="url(#gradient)" />
          </svg>

["#000000", "#001800", "#274d00", "#688300", "#a9b900"]

// https://grabient.com/_gH0gGmgAAgZIgVMgAAgBlgBkgBlgKZgKugAA?style=linearGradient&steps=5&angle=135
// cosine gradient palette — https://iquilezles.org/articles/palettes/
const float STEPS = 5.0;
const float ANGLE = 135.0;

vec3 palette(float t) {
    vec3 a = vec3(0.500, 0.422, 0.000);
    vec3 b = vec3(1.608, 1.356, 0.000);
    vec3 c = vec3(0.101, 0.100, 0.101);
    vec3 d = vec3(0.665, 0.686, 0.000);
    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);
}

[
  [0.500, 0.422, 0.000],
  [1.608, 1.356, 0.000],
  [0.101, 0.100, 0.101],
  [0.665, 0.686, 0.000]
]

Gradient palette editor — #000000 to #a9b900