Oh no! They sky is falling!
Every league I've refereed in has permitted multiple coloured shirts - usually there are 2 or 3 shirts that are expected.
Each short costs about as much as a match fee, or less.
And given that most referees will want to have a few shirts anyway, why not have it in multiple colours? In that sense it doesn't really add to the expense.
In Australia though, even in winter it's good to have the option of a colour that's cooler than black. Also minimises clashes - some teams have have a 'kinda darkish' blue that may not clash during the day but clash in the reduced contrast of night. Also helps with keepers.
Sure, all that can be averted as long as teams don't wear black, or navy.....or even grey......or oven those black and white strips with a solid back where the number is...............
but it's nice being able to stick your head out, see that one keeper is wearing a navy shirt, so you choose one of your other colours so you don't have to worry about putting a team out.
Sure, it's not perfect. Sometimes not everybody has all the colours, so you'll choose to wear blue when 2/3 of you have black and make the team with blue change, things like that. And of course some referees can be *****s about the colours.
But overall, from everything I've heard on here I've always been really glad that I've had flexibility of colours.
Sky blue is the primary colour in my region, burgundy in my previous region.