change color during a loop

[21did21]

Hello world,

i have K curve on a plot and i want to change the color for each curves but i don't know how i can made this

Me code it's here:

for ( int k = 0 ; k < NbOfCurve ; ++k )
    {
            mycurve[0+k*nombreDoublePlot]->attach( myPlot1 );
            mycurve[0+k*nombreDoublePlot]->setStyle( QwtPlotCurve::Dots );
            mycurve[0+k*nombreDoublePlot]->setPen( QPen( Qt::blue, 2) );
}

for ( int k = 0 ; k < NbOfCurve ; ++k )
    {
            mycurve[0+k*nombreDoublePlot]->attach( myPlot1 );
            mycurve[0+k*nombreDoublePlot]->setStyle( QwtPlotCurve::Dots );
            mycurve[0+k*nombreDoublePlot]->setPen( QPen( Qt::blue, 2) );
}

To copy to clipboard, switch view to plain text mode 

This code plots all the curve in blue, however i want differents color for each iteration

can you help me please