Remove #N/A in vlookup result
Solution 1:
If you only want to return a blank when B2 is blank you can use an additional IF function for that scenario specifically, i.e.
=IF(B2="","",VLOOKUP(B2,Index!A1:B12,2,FALSE))
or to return a blank with any error from the VLOOKUP (e.g. including if B2 is populated but that value isn't found by the VLOOKUP) you can use IFERROR function if you have Excel 2007 or later, i.e.
=IFERROR(VLOOKUP(B2,Index!A1:B12,2,FALSE),"")
in earlier versions you need to repeat the VLOOKUP, e.g.
=IF(ISNA(VLOOKUP(B2,Index!A1:B12,2,FALSE)),"",VLOOKUP(B2,Index!A1:B12,2,FALSE))
Solution 2:
if you are looking to change the colour of the cell in case of vlookup error then go for conditional formatting . To do this go the "CONDITIONAL FORMATTING" > "NEW RULE". In this choose the "Select the rule type" = "Format only cells that contains" . After this the window below changes , in which choose "Error" in the first drop-down .After this proceed accordingly.