Hi, shashirekha
Thanks for contacting us.
You can go to Theme Options > Styling Options> Primary Color: black > then click Save& Generate CSS button
We have made this action on your website, but when clicking Save & Generate CSS > it meets the issue. Because your PHP settings are too small.
Please follow this topic learn more about how to fix this issue:
https://yolotheme.com/forums/topic/i-cannot-save-save-generate-css/
And don't forget to contact provider hosting about this issue.
Please check, then feedback to us soon.
Best Regards,
YoloTheme