Fixed color to black for Contours in HoloViews_Introduction
Fixed color to black for Contours in HoloViews_Introduction

ioam/holoviews,mjabri/holoviews,mjabri/holoviews,basnijholt/holoviews,basnijholt/holoviews,basnijholt/holoviews,vascotenner/holoviews,mjabri/holoviews,vascotenner/holoviews,vascotenner/holoviews,ioam/holoviews,ioam/holoviews