Color Mandatory Fields doesn't show

I have a relatively complex form with a number of "User Entered - Required" fields.    In global settings for Form Validation there are checks for the first three items, namely 'Show Dialog Message', 'Color Failed Fields', and 'Color Mandatory Fields'.   In 'Color Mandatory Fields' I have the checkbox checked for 'Color mandatory fields that are not filled-in'.

At present the first two work like a champ when I trigger them using the execValidate function.   However, I was hoping that I could more nicely alert the user to mandatory fields through the 'Color Mandatory Fields' functionality.

How does one trigger 'Color Mandatory Fields' so it shows?

Thanks!