%Rotated Ellipsis, C(\cx,\cy)
\pgfmathparse{0.5} \let\CX\pgfmathresult;
\pgfmathparse{1} \let\CY\pgfmathresult;

%Last angle (starts with 0)
\pgfmathparse{135} \let\Angle\pgfmathresult;

%Number of Ellipsis to draw
\pgfmathparse{10} \let\N\pgfmathresult;

%Half-axis \a \and \b
\pgfmathparse{2} \let\a\pgfmathresult;
\pgfmathparse{1} \let\b\pgfmathresult;

%Size of coordinate system
\pgfmathparse{1.2*max(\a,\b)} \let\size\pgfmathresult;


%Base colors
\definecolor{color1}{rgb}{1,0,0}
\definecolor{color2}{rgb}{0,0,1}

%Calculate color factor: percentage rounded
\newcommand{\Percentage}[2]
{
  \pgfmathparse{int(round(100*#2/#1))}
  \let\percent\pgfmathresult;
}

%Calculate color factor: percentage rounded
\draw[-Latex,very thin] (\CX-\size,0) -- (\CX+\size,0) node[right] {$x$};
\draw[-Latex,very thin] (0,\CY-\size) -- (0,\CY+\size) node[above] {$y$};

%Center
\coordinate (C) at (\CX,\CY);

\pgfmathparse{\Angle/\N} \let\dAngle\pgfmathresult;

%Calculate color factor: percentage rounded
\foreach \n in {0,1,...,\N}
{
    \pgfmathparse{\n*\dAngle} \let\Angle\pgfmathresult;
   
    \Percentage{\N}{\n}
    \tikzstyle{Curve}=[
       domain=-180:180,
       smooth,
       variable=\t,
       color=color1!\percent!color2
    ];

    \draw
       [
          Curve,
          %rotate=\Angle,
          rotate around={\Angle:(C)}
       ]
       plot
       (
          {\CX+\a*cos(\t)},
          {\CY+\b*sin(\t)}
       );
}
