Stuck on color for the pricing table :/

Hi,

I know there are a lot of threads with similar questions but I didn’t find the answer till now.

Default:

My working change:
.main_color .pricing-table li.avia-heading-row {
background: #cc3333;
}

My not working try ;) :
.pricing-table li:nth-child(odd){
background-color: #fcfcfc;
}

And this is what I want:

When I do the change online with chrome, it is working without !important and so. But if I put this to the cumston.css it is not working :/

This is what happens:

.main_color .pricing-table li.avia-heading-row {
background: #cc3333!important;
}
.pricing-table li:nth-child(odd){
background-color: #fcfcfc!important;
}