Part of the AR Foundation DepthGradient shader for Unity

DepthGradient.shader

fragment_output frag (v2f i)
{
    UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(i);

    // Sample the environment depth (in meters).
    float envDistance = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.texcoord).r;

    real lerpFactor = (envDistance - _MinDistance) / (_MaxDistance - _MinDistance);
    real hue = lerp(0.70h, -0.15h, saturate(lerpFactor));
    if (hue < 0.0h)
    {
        hue += 1.0h;
    }
    real3 color = real3(hue, 0.9h, 0.6h);

    fragment_output o;
    o.color = real4(HSVtoRGB(color), 1.0h);
    return o;
}