FPGA VGA driver not working

I am not really sure what is wrong with my code bellow for a vga. All I want the program to do is display a solid color on the monitor. I want to use the switches on my card to change the color displayed. I ran the simulation and all the hsync and vsync signals seem to be as expected. When I flick the switches I get a short pulse of color on the display and then it goes black. Anyone know what is wrong with this code?

module vga(output reg [3:0] red, green, blue,
           input [15:0] sw,
           output hsync, vsync, 
           input clk);
    wire vga_clk; //25.203 Mhz
    vga_clk_gen gen(.clk_in1(clk), .clk_out1(vga_clk));

    reg [9:0] hpx = 0, vpx = 0;
    reg [9:0] next_hpx, next_vpx;
    reg [3:0] next_red, next_green, next_blue;

    assign hsync = !(hpx >= 660 && hpx <= 756);
    assign vsync = !(vpx >= 494 && vpx <= 495);

    always @(posedge vga_clk) begin
        hpx <= next_hpx;
        vpx <= next_vpx;
        red <= next_red;
        green <= next_green;
        blue <= next_blue;
    end

    always @* begin
        next_red = sw[3:0];
        next_blue = sw[7:4];
        next_green = sw[11:8];
        next_vpx = vpx;

        if(hpx == 800) begin
            next_hpx = 0;
            if(vpx == 525)
                next_vpx = 0;
            else
                next_vpx = vpx + 1;
        end else begin
            next_hpx = hpx + 1;
        end
    end
endmodule