colour fill with generative fill

HI can someone help me I am trying to create some product shots and I want them all to have the same colour background, I want to do it with generative fill, as it retains the shadows etc, but if I put in dark beige for example, then each product shot has a different tone of beige it is not uniform.  But generative fill does not seem to understand colours like #eae6e0 which is the colour i want to use.  

Any ideas what the prompt would be to have exactly the same colour beige on each product shot, or is there another way of doing it without generative fill....

thanks in advance for any help...