:checked follows the current state of the selection

Useful to know

:checked selects checked checkbox and radio controls, as well as selected option elements. The state changes when the user interacts. [1]

Example: input:checked + label { font-weight: bold; }. It works when label is the immediate next neighbor. The [checked] selector checks the presence of the HTML attribute and is not equivalent to the current state. Don't just use a color change to show the choice; leave a comprehensible sign or the appropriate native control. Thus, the visual feedback corresponds to the real value.