colab not employing css

When running jupyter on my own machine, the code below (first cell) affects all subsequent cells that reference the css rule, i.e., it works as expected. When I run it in colab, it has no effect. Is there an equivalent form that will work with both local and colab jupyter environments?

%%html
<style>
.h1_cell {
    box-sizing: border-box;
    padding-top:5px;
    padding-bottom:5px;
    font-family: "Times New Roman", "Georgia", "Serif";
    font-size: 125%;
    line-height: 22px; /* 5px +12px + 5px */
    text-indent: 15px;
    background-color: #fbfbea; //#e6e6e6;
    padding: 10px;
}
</style>

Subsequent markdown cells have a header of

<div class=h1_cell>