On the main page, there is a large section under the header that contains Archives and Categories. How do I remove/hide this?

I’ve looked in widgets and customise.

I am currently using the GridMode free version.

I’m trying to change the colour of the header from the present colour to another colour like white, but it’s not possible since there is no provision to do that in the settings. How can I change the colour. Also, i want to remove the search box from the header; how do I go about that? Thanks