1.codigo

<textarea style="overflow: hidden;  border:1px dashed :#84FFC1;   background:#DDFFEE; width: 200px; height: 50px; font-color: #84FFC1;  font-size: 12px; font-family: arial ' sans serif ';" onfocus="this.select()" onmouseover="this.focus()">CONTEÚDO DA SUA   CAIXINHA

2 codigo

  <textarea cols="25" name="textarea" onfocus="this.select()" onmouseover="this.focus()" rows="3" style="background-color: #FF0000; color: rgb(0, 0, 0);"

    wrap="soft">  CAIXA DE TEXTO HTML

Pode mudar a cor do background