A set of {}
is missing:
std::vector<Vertex> data =
{ // for the vector
{ // for a Vertex
{0.0f, 0.0f, 0.0f}, // for array 'position'
{0.0f, 0.0f, 0.0f, 0.0f} // for array 'color'
},
{
{0.0f, 0.0f, 0.0f},
{0.0f, 0.0f, 0.0f, 0.0f}
}
};