There are two ways to specify text formats such as styles, colors, font and font size. And one supersedes the other.
You can select text inside a field and use the formatting tool bar to format the data inside the field. You can dopy and paste text into the field. This formats the data in the field and only formats the data in this one field of one record. Each record can have different text with different formatting in this field, but that formatting for that one record will be visible on any layout that refers to this record.
You can enter layout mode and as you have described, specify formats for the data in the field. This applies to this field on this one layout for all records displayed, but the formatting to data in the field, the first option I described, supersedes this formatting.
To get the formatting specified for the layout to work, you have to remove the formatting applied directly to the data. There are several options for that:
Use this auto-enter calcualtion:
TextFormatRemove ( Self )
And clear the "do not replace existing values.." check box.
This will clear the formatting for all new records, but existing records are not affected. This both clears the formats from pasted text and reverts any formatting applied to the text while in browse mode via the formatting bar.
To clean out the formatting for existing records, Show All Records and use this same function with Replace Field Contents.
And sometimes, you need that data formatting to be preserved for some uses while you want a uniform format on another layout. You can define a calculation field to use for this purpose defined as:
TextFormatRemove ( TextFIeldNameHere )
And then you can use this field on layouts where you need the consistent formatting.