Fix a typo in ColorSpace.get

Test: I1759437bf620868706be0aadce2250ac9194ca7d

The intent is that an index that does not match a Named ColorSpace will
throw an IllegalArgumentException, so make that true for
Named.values().length, which does not correspond to one.

Also, update the Exception message to make it clear that the last index
is exclusive.

Change-Id: I015b7ee6274873cc329653473ead04b08f1cd55f