Monitor with orange blinking light

I have a VGA connector Mitsubishi Diamond pro monitor attached to a DVI port of my graphics card by a VGA/DVI convertor. Last night I put the pc in sleep mode. This morning I used keyborad to wake it up and even though the pc was back up, the monitor is blinking orange and staying blank. I turned the monitor off and on again, first green light comes on and then it goes back to blinking orange. I tried turning the pc on and off and result was the same. I tried different monitor and that works so it's definitely the monitor that has gone to sleep. How can I wake it up? I appreciate all your help. Thanks.