// color = texture
C3D_TexEnvSrc(e, C3D_Both, texSrc, GPU_PRIMARY_COLOR, GPU_PRIMARY_COLOR);
C3D_TexEnvFunc(e, C3D_Both, GPU_MODULATE);
e++;

// color = color * 0.5 + 0.5
C3D_TexEnvSrc(e, C3D_Both, GPU_PREVIOUS, GPU_CONSTANT, GPU_CONSTANT);
C3D_TexEnvFunc(e, C3D_Both, GPU_MULTIPLY_ADD);
C3D_TexEnvColor(e, 0x00808080);
e++;

// color = dot(color*2.0-1.0, grayscale_vec*2.0-1.0)
C3D_TexEnvSrc(e, C3D_Both, GPU_PREVIOUS, GPU_CONSTANT, GPU_PRIMARY_COLOR);
C3D_TexEnvFunc(e, C3D_Both, GPU_DOT3_RGB);
C3D_TexEnvColor(e, 0x008ECAA6);
e++;

// color *= blue_tint
C3D_TexEnvSrc(e, C3D_Both, GPU_PREVIOUS, GPU_CONSTANT, GPU_PRIMARY_COLOR);
C3D_TexEnvFunc(e, C3D_Both, GPU_MODULATE);
C3D_TexEnvColor(e, 0x00FFC0C0);
e++;