Hello @beho83
To modify the background of the validation dialogs, you can enter a block of styles similar to the following one into the “Customize Form Design” attribute in the “Form Settings” (https://resources.developers4web.com/cff/images/documentation/form-settings-tab.png)
form #fbuilder .fields .dfield div.cpefb_error{background:green !important;border-color:green !important;}
form #fbuilder .fields .dfield div.cpefb_error::after{border-bottom: 10px solid green !important;}
The checkbox and radio button are elements you cannot customize like other HTML tags. The alternative is to hide them and emulate their states:
#fbuilder .fields input[type="checkbox"],
#fbuilder .fields input[type="radio"]{display:none;}
#fbuilder .cff-radiobutton-field:not(.cff-switch-container) .dfield input+span::before,
#fbuilder .cff-checkbox-field:not(.cff-switch-container) .dfield input+span::before{content:"?";font-size:16px;line-height:16px;font-weight:bold;text-align:center;width:16px;height:16px;display:inline-block;background:white;color:white;margin-right:10px;}
#fbuilder .cff-radiobutton-field:not(.cff-switch-container) .dfield input+span::before{border-radius:20px;}
#fbuilder .cff-radiobutton-field:not(.cff-switch-container) .dfield input:checked+span::before,
#fbuilder .cff-checkbox-field:not(.cff-switch-container) .dfield input:checked+span::before{color:#3cce88;}
Best regards.