End portal shader defines 16 colors but only uses 15 of them

(this bug is much older than 1.21.7, but I have no way to include that here)
The end portal shader file rendertype_end_portal.fsh uses the following code to pass the various end portal textures to glsl to render each pixel:

void main() {
    vec3 color = textureProj(Sampler0, texProj0).rgb * COLORS[0];
    for (int i = 0; i < PORTAL_LAYERS; i++) {
        color += textureProj(Sampler1, texProj0 * end_portal_layer(float(i + 1))).rgb * COLORS[i];
    }
    fragColor = apply_fog(vec4(color, 1.0), sphericalVertexDistance, cylindricalVertexDistance, FogEnvironmentalStart, FogEnvironmentalEnd, FogRenderDistanceStart, FogRenderDistanceEnd, FogColor);
}

When it references the COLORS array of vec3 colors, it first references the first one as a tint to the end background texture. Then it goes through 15 layers and transforms them and tints colors using array ids 0-14. However, the COLORS array defines 16 colors. COLORS[15] is a valid color, and likely one that is intended to be used, but it is never accessed when drawing the textures.

There are three possibilities, none of which is currently happening:
A. There are supposed to be 16 end portal moving layers, making the first layer use the same color as the tint to the background texture. This would mean changing the integer variable PORTAL_LAYERS from 15 to 16 and then it would add one more layer and use all of the colors.
B. There are supposed to be 15 end portal moving layers, but they currently each reference the wrong color. COLORS[i] should be switched to COLORS[i + 1] and then each color is shifted deeper from its current state and a new blueish color is added as the topmost color.
C. There are supposed to be 15 end portal moving layers, and they are referenced as intended where the background and deepest layer both have the same tint, and the 16th color is redundant.

I have attached a before and after picture of making use of change B, because that seems like the most likely intended behavior to me.