Getting Excel Cell Properties in Bulk

I don't think you can get those properties as an array because of how Excel stores that information. Excel does not store formatting for each cell individually but rather stores a particular blend of formats along with an internal "list" of the ranges that use that format.

You can get a sense of how the formatting is stored by creating a small test file with various formats and saving it as XML format (in 2010 at least, you need to use "XML Spreadsheet 2003").

This article may also help.

"I want to find which cells are colored a certain way"

in VBA you can run a quick routine using the Find method that searches by format. For example to find all cells with the same cell font colour and interior colour as the cell in A1. I presume you can use something similar in VSTO

Sub FindFormat()
    Dim rng1 As Range
    Dim rng2 As Range
    Dim strAddress As String
    With Application.FindFormat
        .Interior.ColorIndex = [a1].Interior.ColorIndex
        .Font.Color = [a1].Font.Color
    End With
    Set rng1 = Cells.Find("", [a1], xlFormulas, , , , , , True)
    If Not rng1 Is Nothing Then
        strAddress = rng1.Address
        Set rng2 = rng1
        Do
            Set rng1 = Cells.Find("", rng1, xlFormulas, , , , , , True)
            Set rng2 = Union(rng1, rng2)
        Loop While rng1.Address <> strAddress
        MsgBox "Range similar format to A1 is " & rng2.Address
    End If
End Sub