The grid spacing between the lines is determined by the step parameters that you give the axis. Therefore, if you need basic horizontal lines / ticks for each integer and small horizontal lines for each 0.25, you can do:
chart1.addAxis("y", { ... majorTickStep: 1, minorTickStep: 0.25 });
To change the color of the grid lines, the only way I know is to manipulate the theme you are using.
var myTheme = dojox.charting.themes.PlotKit.blue; // Or any other theme myTheme.axis.majorTick.color = "green"; myTheme.axis.minorTick.color = "red"; chart1.setTheme(myTheme);
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