Background color in an 'answer' dialog?

[Graham Samuel]

I have created hundreds of LC ‘answer’ commands in my time, and as far as I can remember they all had white backgrounds. Recently I accidentally created one with a lovely red background, showing up in standalones on both Mac High Sierra and Windows 7. Well, it would be lovely if i wanted it that way… 

When I edited some lines of script, the background reverted to white! 

There is nothing in the LC Dictionary suggesting that this color can be set - can anyone say what I did and how to control the color?

Graham