Twilight to dirty blue to viridian gradient palette editor

/* https://grabient.com/_gELfw4f-LgGtgYNgLUgBkgBogBlgDLgOcgP1?style=linearGradient&steps=5&angle=135 */

background: linear-gradient(135deg, #64689a 0.000%, #538195 25.000%, #42908c 50.000%, #31947f 75.000%, #208e6d 100.000%);

<svg xmlns="http://www.w3.org/2000/svg" width="800" height="400" viewBox="0 0 800 400" preserveAspectRatio="none">
            <!-- https://grabient.com/_gELfw4f-LgGtgYNgLUgBkgBogBlgDLgOcgP1?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="#64689a" /><stop offset="0.250" stop-color="#538195" /><stop offset="0.500" stop-color="#42908c" /><stop offset="0.750" stop-color="#31947f" /><stop offset="1.000" stop-color="#208e6d" />
              </linearGradient>
            </defs>
            <rect x="0" y="0" width="800" height="400" fill="url(#gradient)" />
          </svg>

["#64689a", "#538195", "#42908c", "#31947f", "#208e6d"]

// https://grabient.com/_gELfw4f-LgGtgYNgLUgBkgBogBlgDLgOcgP1?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(0.267, -0.968, -0.117);
    vec3 b = vec3(0.429, 1.549, 0.724);
    vec3 c = vec3(0.100, 0.104, 0.101);
    vec3 d = vec3(0.203, 0.924, 1.013);
    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);
}

[
  [0.267, -0.968, -0.117],
  [0.429, 1.549, 0.724],
  [0.100, 0.104, 0.101],
  [0.203, 0.924, 1.013]
]