I meant the structure on either side of the propellent tanks. It's supposed to be coloured red.
Well, it's supposed to be
glowing red during engine use and some time thereafter. It's not their natural color, it's because they're literally glowing hot. Whether or not that effect is doable depends on whatframework gattispilot is using to create the thing, though.
Also, the mirror shields at the rear end would also serve as a kinetic shield against relativistic dust once the ship is decelerating, that's why there's multiple layers of them. I'm not sure what they'd use during the acceleration phase for that, though. Merely the solar sail seems insufficient, you need more than one layer for a
whipple shield.
The original design concept the venture star was inspired by uses droplet radiators that create quite an effective shield in combination with the magnetic field from the antimatter engines, but the venture star doesn't have those. Which
does make sense, since they're only useful during the acceleration phase, during which the venture star would be propelled by lasers, not its engines, so it wouldn't need the radiators. As far as I know there are no depictions of the venture star in its acceleration configuration with the lightsail unfolded.
The whole design came out of the
Valkyrie concept, if anybody's interested in the details. Just that in the movie they decided to instead name the shuttles like that, maybe as a reference.