Any alternative colors/skins for captchator images?

First of all, thank you for this service - it is extremely useful.

I’m using Captchator for a site I’ve built for a client, and he seems to
think that the captchas are too difficult to read given the colors.

Are there any alternative image types to pull for the captchas?

Is there perhaps any way that I can influence the images on my side to
make them more readable? (I doubt it)

Thanks,
Wes