Questions about fine-tuning styles in CFF

Hi!
Please tell me how to change the pop-up error style for fields?
I am interested in the background color, font and outline of the field.

These tricks don’t work for me:

/* 
==============================================================================
Styles for fields with errors
===================================================================================== */ /* Fields with errors (outline highlighting) */ 
.custom-fieldname7 .field[aria-invalid="true"], 
.custom-fieldname7 .field.error { 
    border-color: #866552 !important; /* Error border color */
    transition: border-color 0.3s ease;
}

/* 
===============================================================================
Error popup styles
============================================================================ */ 
.custom-fieldname7 .errormsg { 
    background-color: #866552 !important; /* Message background color */ 
    color: #D2C8BC !important; /* Message text color */
}

Also please tell me how to exclude the first value in the drop-down menu from the selection (for example, when it is a preset value).

<option value="" disabled selected>Preset value</option>

Thank you in advance for your answer.