If there are no better ways on offer, you can change the "blue" mode to have a white background...
In the weather-screen-blue-narrow.css file, the definition for .column-dark has a background-color of #F1F8fE defined. Remove that background colour if you want it white.
.column-dark {
color: black;
background-color: #F1F8FE;
}
and the same for the wide format in the file weather-screen-blue-wide.css
It would be better to add a "white" colour option though and make that the default, but that is way outside my knowledge of how that template works.
There may other side effects of that hack on other pages though, so check them all out if you make the change.