Find line of text beginning with spaces

[zm23]

I have text with manual line breaks and some lines begins with for example three spaces before first word in line.

If that would make it easier, I can change manual line breaks into paragraph endings.

I want to find this text and replace with the same text but add some formatting (for example color or italic). The trouble is that in other parts of text some lines begin with different number of spaces and I don’t want to change them. So, three dots and after that any letter is here as a recognition pattern and some repetition in Replace of what is in Find must be used.

I suppose I need some regex.

[LeroyG]

Find: (?m)^[:space:]{3}[^ ].*

(?m) Control the behavior of “^” and “$” in a pattern. By default these will only match at the start and end, respectively, of the input text. If this flag is set, “^” and “$” will also match at the start and end of each line within the input text.
ICU Regular Expressions

Also works with:
(?m)^[:space:]{3}[^\h].*
(?m)^[:space:]{3}[^\s].*
(?m)^[:space:]{3}[\S].*
(?m)^[\s]{3}[\S].*