There are several sources of browning in a typical pizza crust. One is protein, as you mentioned. During baking, the protein from the flour in the dough reacts with reducing sugars, mainly glucose, lactose and fructose, to produce browning through what is called the Maillard reaction, named after the French scientist who studied the phenomenon. The reducing sugars come mainly from the enzymatic (alpha amylase) breakdown of damaged starch in the flour. The KASL has more protein than the Extra but it also has more damaged starch and it is a malted flour. The malt, either in the form of barley malt or fungal amylase (usually added by the miller at the factory but also sometimes by bakers), increases the enzymatic breakdown of damaged starch into sugar to be available at the time of baking to promote browning.
The Caputo Extra, as well as the other Caputo flours, are less prone to starch damage than our domestic flours and they are unmalted. So they are not the best candidates for producing copious amounts of sugar in a short period of time for browning purposes. They will, however, tolerate fairly long periods of fermentation under the proper temperature/time conditions and produce residual sugar for browning purposes. But even under the influence of high oven temperatures the finished crusts will not be golden brown as we experience with flours like the KASL, as you will see from the photos of authentic Neapolitan pizzas that pizzanapoletana and others have posted. Remember also that it can take but a minute or two to bake a Neapolitan pizza in a wood-fired oven, so you won't get the same type of browning as in a lower temperature oven, such as a home oven. FYI, damaged starch is starch that is damaged either as a result of poor wheat crops or as a result of damage during milling, or both. It may sound like damaged starch is a condition to be avoided but, without sufficient damaged starch, it would take longer to make our pizzas.
It is possible to use both diastatic and non-diastatic malt with a flour. The diastatic malt is used to increase enzymatic performance, and its net effect is to increase the amount of residual sugar in the dough at the time of baking to increase color in the crust. Non-diastatic malt is only a sweetener and, as in the case of the bagels you mentioned, will increase crust browning during baking (mainly through caramelization of sugar) as well as add sweetness to the finished crust. You can also use regular sugar, and you can also use dry powdered milk (in includes lactose) provided it is the right form of milk (a special baker's grade powdered milk). It is also possible to increase the level of damaged starch in the flour, by running the flour through specialized equipment designed for this purpose. I even tried running the Caputo Pizzeria flour through the whirling blade of my food processor to do the same thing.
I have tried all of the above approaches, and they were chronicled in the A16 thread. I thought dairy whey was the most effective way of increasing crust browning of the Caputo flour in a home oven application, although it will have other effects on the dough as I previously mentioned. I also found that simply oiling the unbaked rim of the dough helped with browning. Using the broiler element for about a minute or so to finish baking also helped.
If there is a magic bullet that allows us to make a Neapolitan crust in a home oven like that made in a high-temperature wood-fired oven, I haven't found it.