Styling Header

To set style for a specific cell of the header you should use the following technique:

General styling of the header

<style>
  .my_style{
    background-color:#FFAAAA;
  }
</style>

<script>
webix.grid({
  columns:[
    { id:"title",  header:{ text:"Film title", css:{ "background":"#AFA"}} },
    { id:"votes",  header:{ text:"Votes",      css:"my_style"} }
  ]
});
</script>

Related sample:  Header Styling