What are the secrets of RGBV that have yet to come up? (Servo+, feeling colorful)
None of their favorite colors are the colors that they're wearing. Link's favorite color, before the split, was yellow. RGBV's favorite color is still yellow, but there's a silent pact that none of them get to wear it because otherwise that would be unfair. They've all, separately, grown fond of their assigned color though. This will probably result in Link-the-composite wearing a near-literal color explosion to compensate, once the time comes to put the Four Sword back
Red has a running list of potential names in his head In Case Of Merge, because Link-the-composite can't be called Red! Similarly, Vio has a running list of potential synonyms In Case Of Red Wanting Names In Case Of Merge
If they lean into the Four Sword connection, they could pull a Four with very little effort. Full synchronization and everything. This does not, however, mean that they want to
Technically, all four of them can break the walls. It's just that Blue is the only one brazen enough to do it on purpose. Red just hasn't thought about doing it himself, Green is secretly tempted but too responsible to try, and Vio actually is against it
Of course, by these ratios, Link-the-composite would most likely carry on Blue's legacy, because there's not enough real opposition to stop that part of him
They are not very good singers or musicians
On the other hand, they're pretty decent dancers
The Four Sword split them evenly, but not necessarily in a way that would make sense. For example, Red is the one with the majority of the cooking skills, but Green is the one with the patience and the focus to actually stand in a kitchen and make something
They have a decent amount of spelunking experience and are among the few Links in the group who will willingly hop into a strange cave with no questions asked
The existence of Moon Gates in their native Hyrule have effectively skewed their entire perception of how common alternate/dark worlds are. Oh, multiple other Links have one of those too? Must be pretty normal then. (Spoiler: it is not)
They don't like to be cold. Warm-weather boys all the way
Their eyes have changed color to match their color. Vio has violet eyes, Blue has blue eyes, etc. Ironically, for all that Green can usually claim keeping their original color scheme, Link-the-composite did not have green eyes. (They were blue)
There is no such thing as a consequence-free soul merge, and therefore there is also no such thing as a consequence-free soul split. There's an event-horizon of no return with the Four Sword, and if they cross it they're effectively going to be a system when they merge back into Link-the-composite. They don't know this (nobody documented it), and they haven't crossed it yet, but...
Despite occasional evidence to the contrary, all four of them are actively and constantly making sure that the other three are within sight at all times. If it goes too long, they get twitchy. There's a little Four-Sword-influenced voice in their heads going 'those are your other pieces, do you know where they are? do you know they're safe? keep them close. don't lose them.' It's a safety feature so that the wielder is less likely to lose a facet permanently, because three remaining pieces trying to make up what was previously a four-pieced person... doesn't go well. It'd get classified as co-dependency, if they weren't literally pieces of a whole.
And lastly, they're amazing at group strategies - but only within their specific group. Left to their own plans, the four of them are the most in-sync team imaginable, outside of the actual Four. Add in additional Links and ask them to make a plan, and they're probably going to forget that there's other people they need to account for. This is why Green is not a leader of the whole Chain, but is still the de-facto leader of his Four-Sword-subset.