DirectX hlsl shader does not process color - c++

Question

Just starting with DirectX. I have a pixel shader to combine a texture and a color. The texture part works fine. But the color part does nothing. I must be missing something.
I do not get errors. The code "input.color" is 0 (I think, I can't check inside the shader code with the debugger).
Does anyone have any tips to what the problem might be?
Thank you.
// Shader code:
struct PixelInputType
{
float4 position : SV_POSITION;
float2 tex : TEXCOORD0;
float4 color : COLOR;
};
float4 TexturePixelShader(PixelInputType input) : SV_TARGET
{
float4 textureColor;
textureColor = shaderTexture.Sample(SampleType, input.tex); // This works fine.
textureColor += float4(0.0f, 0.25f, 0.0f, 1.0f); // This works fine, makes texture greeny.
textureColor += input.color; // This does not work. Does nothing.
return textureColor;
}
// DirectX code:
struct VertexType
{
DirectX::XMFLOAT4 position;
DirectX::XMFLOAT2 texture;
DirectX::XMFLOAT4 color;
};
//
D3D11_INPUT_ELEMENT_DESC polygonLayout[3];
polygonLayout[0].SemanticName = "POSITION";
polygonLayout[0].SemanticIndex = 0;
polygonLayout[0].Format = DXGI_FORMAT_R32G32B32A32_FLOAT;
polygonLayout[0].InputSlot = 0;
polygonLayout[0].AlignedByteOffset = 0;
polygonLayout[0].InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
polygonLayout[0].InstanceDataStepRate = 0;
polygonLayout[1].SemanticName = "TEXCOORD";
polygonLayout[1].SemanticIndex = 0;
polygonLayout[1].Format = DXGI_FORMAT_R32G32_FLOAT;
polygonLayout[1].InputSlot = 0;
polygonLayout[1].AlignedByteOffset = D3D11_APPEND_ALIGNED_ELEMENT;
polygonLayout[1].InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
polygonLayout[1].InstanceDataStepRate = 0;
polygonLayout[2].SemanticName = "COLOR";
polygonLayout[2].SemanticIndex = 0;
polygonLayout[2].Format = DXGI_FORMAT_R32G32B32A32_FLOAT;
polygonLayout[2].InputSlot = 0;
polygonLayout[2].AlignedByteOffset = D3D11_APPEND_ALIGNED_ELEMENT;
polygonLayout[2].InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
polygonLayout[2].InstanceDataStepRate = 0;
//
std::vector<VertexType> vertices;
vertices[0].position = DirectX::XMFLOAT4(-1.0f, -1.0f, 0.0f, 0.0f);
vertices[0].texture = DirectX::XMFLOAT2(0.0f, 1.0f);
vertices[0].color = DirectX::XMFLOAT4(0.0f, 1.0f, 0.0f, 1.0f);
vertices[1].position = DirectX::XMFLOAT4(0.0f, 1.0f, 0.0f, 0.0f);
vertices[1].texture = DirectX::XMFLOAT2(0.5f, 0.0f);
vertices[1].color = DirectX::XMFLOAT4(0.0f, 1.0f, 0.0f, 1.0f);
vertices[2].position = DirectX::XMFLOAT4(1.0f, -1.0f, 0.0f, 0.0f);
vertices[2].texture = DirectX::XMFLOAT2(1.0f, 1.0f);
vertices[2].color = DirectX::XMFLOAT4(0.0f, 1.0f, 0.0f, 1.0f);
//
D3D11_BUFFER_DESC vertexBufferDesc;
vertexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
vertexBufferDesc.ByteWidth = sizeof(VertexType) * m_vertexCount;
vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
vertexBufferDesc.CPUAccessFlags = 0;
vertexBufferDesc.MiscFlags = 0;
vertexBufferDesc.StructureByteStride = 0;