What is the vector X, Y, Z on the left side of the arrow? And is this matrix a fixed one?

It is the value of color represented in XYZ space. I don't think it is a fixed one. Different color has different value for this matrix.

What is the vector X, Y, Z on the left side of the arrow? And is this matrix a fixed one?

It is the value of color represented in XYZ space. I don't think it is a fixed one. Different color has different value for this matrix.