Hi!
dat.GUI is a separated control library and, IMHO, it’s out of the scope of this forum, but…
As any control, it contains many html-elements that you can style with css.
Using element inspector, you can see what style applied to what element:
Originally, style for checkboxes is:
.dg .c input[type="checkbox"] {
margin-top: 9px;
}
I’ve simply added some lines right in the inspector and got those red corners on checkboxes.
Maybe this reply will give you some ideas with styling of that control.