you could use this:

    var myStyle= {fillColor: "#ff0000"};
    			
    			 var BounderyshpLayer = new OpenLayers.Layer.Vector({
    			 projection: new OpenLayers.Projection('EPSG:3826'),
    			 style: myStyle
    			 });

see:
http://jsfiddle.net/expedio/2xvfbtdw/

or even use a stylemap with different style for default and select:

    var defStyle = {fillColor: "#ff0000",strokeColor: "green", strokeOpacity: "0.7", strokeWidth: 3, cursor: "pointer"};
            var sty = OpenLayers.Util.applyDefaults(defStyle, OpenLayers.Feature.Vector.style["default"]);
            
    		var sm = new OpenLayers.StyleMap({
                'default': sty,
                'select': {strokeColor: "red", fillColor: "green"}
            });
    		
    		var BounderyshpLayer = new OpenLayers.Layer.Vector({
    			 projection: new OpenLayers.Projection('EPSG:3826'),
    			 styleMap: sm,
    			 });

see: http://jsfiddle.net/expedio/yxr5wdjo/

nice website with Information about the Feature-Style and Stylemap:
http://www.peterrobins.co.uk/it/olstyle.html