Not sure if a Formula could do it but here's an example of a VBA way to pick up multiple matches in a string using a Regular Expression.

[vba]
Sub Multiple_Match_Find()
Dim re As Object
Dim words As String
Dim m

Set re = CreateObject("vbscript.regexp")

words = "Testing Blue is Blue"
With re
.Global = True
.IgnoreCase = True
.Pattern = "Blue"
For Each m In .Execute(words)
MsgBox m.FirstIndex
Next
End With
End Sub[/vba]