change color purple

https://prnt.sc/u0bQvgxDVhNr
please, could you help me to change the color purple. please

Each position in that Spotlight 2 section is set with a class like bg-1 and this class is set with that background:

div#t4-spotlight-2 .bg-1 {
    background: #323183;
    color: rgba(255, 255, 255, 0.5);
}

If you don't want that background color, you can go to Layout settings and remove that class

Or override above css code to adjust background color as you wish.

About back to top button, you can override with this custom css:

#back-to-top {
    background: #323183 !important;
}