Having looked into this I would have to buy a can of spray that I thought that was close to the colour, test spray something then compare against the rocker cover on the bike and only then dismantle, degrease and mask off any required areas before spraying.
I have seen a few likely matches of spray on ebay but I have not taken the step to buy.
I did also see a spare rocker cover on ebay but it was accident damaged so that was quickly ruled out.
If you find a colour that is close let me know as I am interested in doing this.