// input fragment
struct FragIn
{
  float4 color : COLOR0;
};
  
// output fragment
struct FragOut
{
  float4 color : COLOR0;
};
  
// fragment shader main entry
FragOut main(FragIn IN)
{
  FragOut OUT;
  OUT.color   = IN.color; // copy input color to output
  OUT.color.z = 1.0f; // blue component of color = 1.0f
  return OUT;
}