Friend or Foe

My sheep are treating me a bit like an enemy or at least are viewing me that way lately. The cause is I have upgraded to a new chore jacket, duck black vs. the duck brown and torn version. Now when I enter their yard I get the flight response. I am wearing the same winter hat, pants, etc. but find it very interesting that they don't recognize me immediately. They will settle but are uneasy. I speak to them but usually by then someone is already in alarmist mode and it does no good. Is it the color that makes the difference I am wondering? They should come to know me again by lambing and yes they will find out they are still alive and unharmed, and I hope they feel really silly about it. Actually, I am pleased they respond to something new in a survival mode as it is their instinct afterall but seems a bit over-reactive.