Within a chart how do I change the gridlines color and size?


To change the style of the gridlines, you can use CSS as such:
.stx_grid { /* Default Grid */    color:#efefef;    opacity:1;    border-style:solid;     width: 10px;    }
.stx_grid_dark {/* Default Grid dividers */    color:#cccccc;    opacity:.9;    border-style:solid;     width: 10px;    }