Granulated white sugar is highly refined - that is why it is so white. Brown sugars have some residual amounts of molasses left in them - that is why they are brown. The brown solids are not digestible by bees, so they must be pooped out. In winter conditions when flying opportunities are limited, cleansing flights may not be possible, so the bees have to hold it in.
In warmer weather when cleansing flights are not a problem, the solids in brown sugar may not be that big of an issue if the syrup is consumed right away. But, it is always possible that the bees might store some of that brown sugar syrup for later use, so it might still get consumed later during a period when cleansing flight opportunities are limited.
The safest plan is to avoid feeding any sugar other than plain granulated white sugar.
Note that many sugars sold as "organic" have a brown tinge to them. The color is because those sugars are refined to a lesser degree than plain granulated white sugar. So feeding bees "organic" sugar that is not bright white carries the same risks that are noted above.
You have panela which is an unrefined form of sugar, not necessarily the same as what we call brown sugar here in the States which has had molassess added back in to previously refined pure sugar.
While panela is very tasty I wouldn't feed it to my bees because of its lack of purity. (Though since it is usually cheaper in Latin America than granulated, near-white, crystal sugar which is the other common option, I am certain it has been used for bees by somebody, somewhere.)
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