Hi

I think this might be better to resolve the main problem first. If you find yourself wanting to put more than one category form field, then your data structure is wrong. Instead, you need to use custom taxonomies to separate what you held in the one category taxonomy. You can use a free plugin called CPT UI (Custom Post Type UI) to do this.

Then, when you have done this, let me know so that I can look at the form again. The CSS I can see on the form is this:

select option:checked, select option:hover, select option:focus {
    background-color: #D20005;
    background-image: -webkit-gradient(linear,50% 0,50% 100%,color-stop(20%,#D20005),color-stop(90%,#D20005));
    background-image: -webkit-linear-gradient(#D20005 20%,#D20005 90%);
    background-image: -moz-linear-gradient(#D20005 20%,#D20005 90%);
    background-image: -o-linear-gradient(#D20005 20%,#D20005 90%);
    background-image: linear-gradient(#D20005 20%,#D20005 90%);
    color: #fff;
}

Add something like this to your Custom CSS (change the colors as you need, I have left them as they are in this example):

.searchandfilter select option:checked, select option:hover, select option:focus {
    background-color: #D20005;
    background-image: -webkit-gradient(linear,50% 0,50% 100%,color-stop(20%,#D20005),color-stop(90%,#D20005));
    background-image: -webkit-linear-gradient(#D20005 20%,#D20005 90%);
    background-image: -moz-linear-gradient(#D20005 20%,#D20005 90%);
    background-image: -o-linear-gradient(#D20005 20%,#D20005 90%);
    background-image: linear-gradient(#D20005 20%,#D20005 90%);
    color: #fff;
}

As our plugin develops, we will add scripted versions of dropdowns. We currently have one script to run combo boxes (chosen I think), the next version will have 2 scripts for this (we will add select2) and I think these allow more control, but they are combo boxes.

Authors are different from other fields, and this is a result of how WordPress handles them 🙁

Let us say you have 6 authors in total, but in Category A there are only 3 authors. You expect if you select Category A the list of Authors would be come 3, but instead it will stay at 6. At this time, we cannot change this.

The same applies to trying to autodetect an author from the url.

By combo boxes, I see you have used these on the form (the ‘chosen’ type), are you saying that these also cannot be styled in Chrome? For example, the Author box is just so.

I will ask the devs about authors.