Tan Sidewall Tyres

Some sort of cat tyre shine (not black!) Would likely work, or a sealant type wax or polish, even something simple like Mr Sheen lol

nylon bristled dishes brush and some hot water, add a bit of lemon juice or vinegar. Baby wipes are not very environmentally friendly and you could end up using loads. Wipe with toilet tissue at least it can be recycled and still works out cheaper than baby wipes by a lot.

Oh and clean your rims regularly too if you use rim brakes, same method.

+1 for giving baby wipes a try: they clean almost anything.

 I dread to think what they actually do to a bum cheek given some of the grime I've used them to remove - Considering their intended use and claims of no chemicals / kind to skin etc they are remarkably adept at getting all iinds of crapola off all kinds of surfaces. 

A colleague of mine used shoe polish to blacken his sidewalls. I wouldn't recommend it though (I told him so at the time, and warned him to be careful not to get it on his rims if he went ahead - he's still with us, so he heeded the second part at least). 

Edit: I see you have tan sidewalls, so at least with shoe polish you might gert a colour match

I used mcNetts Seamgrip on my Vittoria Corsa's. Kept them super clean.

A quick wipe with baby wipes after each ride keeps em looking clean

Did this with my old Corsa tubs and with my current Rally's

You can get tyre shine in gel form (I'm sure there's a bottle of Meguiars lurking under mysink) and it probably would protect the tyre to some extent but I'd only try it if you have disc brakes. If you have rim brakes and any got on the braking surface  I suspect it would be 'goodbye braking'...