Could probably be more efficient, but seems to work for your example:

Sub ScratchMacro()
'A basic Word macro coded by Greg Maxey, http://gregmaxey.com/word_tips.html, 12/26/2017
Dim strPattern1 As String, strPattern2 As String
Dim oRngCompare As Range, oRng As Range
  strPattern1 = "SPEAKER ONE"
  strPattern2 = "SPEAKER TWO"
  Set oRngCompare = ActiveDocument.Paragraphs(2).Range
  oRngCompare.Start = ActiveDocument.Range.Start
  On Error GoTo lbl_Exit
  Do
    If InStr(oRngCompare, strPattern1) <> 1 Then
      Set oRng = oRngCompare.Paragraphs(1).Range
      oRng.Collapse wdCollapseStart
      oRng.MoveEnd wdCharacter, Len(strPattern1)
      oRng.HighlightColorIndex = wdRed
    End If
    If InStr(oRngCompare.Paragraphs(2), strPattern2) <> 1 Then
      Set oRng = oRngCompare.Paragraphs(2).Range
      oRng.Collapse wdCollapseStart
      oRng.MoveEnd wdCharacter, Len(strPattern2)
      oRng.HighlightColorIndex = wdRed
    End If
    oRngCompare.MoveStart wdParagraph, 2
    oRngCompare.MoveEnd wdParagraph, 2
    If oRngCompare.Paragraphs.Count < 2 Then Exit Sub
  Loop
lbl_Exit:
  Exit Sub
End Sub