The default font size and color for rich text input form in SharePoint

The default font size for rich text input form in SharePoint seems much too small.

How do I change the default settings?

I have already tried to change the CSS file as below.

However, the output does not reflect the below settings.

I also attach the text copy of my CSS file.

.ms-rtestate-write, .ms-rtestate-write p, .ms-rtestate-read p{
font-size: 12pt;
font-family: "Meiryo UI";
color: black;
}