Worksheets can be dragged and dropped into any order required. They can be set up in numeric or alpha order, but doing it by hand is a bother.
Chip Pearson has written some macros that will do the job for you:
Sorting Worksheets In Alphabetical Order
Sorting In Custom Order
Grouping Sheets By Color
Here's the code to sort by tab color:
Sub GroupSheetsByColor() Dim Ndx As Long Dim Ndx2 As Long For Ndx = 1 To Worksheets.Count - 1 For Ndx2 = Ndx To Worksheets.Count If Worksheets(Ndx2).Tab.ColorIndex = _ Worksheets(Ndx).Tab.ColorIndex Then Worksheets(Ndx2).Move after:=Worksheets(Ndx) End If Next Ndx2 Next Ndx End Sub