The RotJ Boba Fett suit is much more colorful than ESB. Blue, red and yellow play prominently in the design of the costume.
The RotJ helmet is very similar to the Pre-pro version.
Key Features of the RotJ Helmet
Weathering is less detailed than ESB. It's more like something that's been banged around for years than something well crafted
Earcaps have a dirty metallic finish.
Visor is smoked grey
Arrows on the forehead are red and blue
Rangefinder lacks the small window found on the ESB helmet
The darker portion of the mandibles is more of a blueish-green than a black
The mandibles are a red brick color
The back of the helmet is a bright blue/green color
Kill stripes are all orange (number of stripes?)
The frame that the key slots are in on the back of the helmet are silver
RotJ Helmet Painting Guide
The overall shape / style of the backpack remains consistent through all the version of Boba, but the paint job changes. The RotJ backpack is quite colorful, a point of contention between RotJ and ESB fans. Like the helmet, the pack looks a lot like the pre-pro version.
Related to the pack is the belt that is visible in some shots. The jetpack harness had a waist belt that used a US Divers Kam EZ-pak buckle, believed to have a sheet of foil tape over the US Divers logo. How this is integrated into the costume varies. Some people have the belt on their harness. Others attach the belt directly to the pack to help secure it against the body.
The overall shape and style of the gauntlets is similar to ESB, except for the flame thrower on the left arm. In ESB it looked like a series of tubes and connectors. Cool looking, but in costuming terms, easily damaged. RotJ replaces it with a sturdy, boxy style.
The RotJ gaunts are a dark red color. The off the shelf spray can color “Claret Wine” by Rustoleum (Branded under Painters Touch or America's Finest) is a good match, if toned down with some black.
There are a number of greeblies on the gauntlets. The keypad on the left arm is from a Casio MQ-1 calculator. You'll also find small pointed darts, a dental expander, switches and LEDs.
The chest armor for RoTJ is lighter in color than the ESB version. Also, there is more weathering and denting.
The skull on Fett's left shoulder changes from film to film. In ESB the tusks of the skull are connected to the skull. In RotJ they are separate.
The RotJ cape is an olive green canvas. It is made from a US Army shelter half. These are readily available at most surplus stores for around $10, but not all have the right stitching. If the one you find doesn't, it's easy enough to sew in a couple of lines.
Brak's Buddy's RotJ Cape Tutorial
This is a topic much debated over at TDH, but to a casual glance at least, the RotJ flight suit looks to be a dirtied up light grey color, vs. bluish tint to the ESB. The dirt is important… a clean Boba just isn't right! The overall pattern of the suit remains the same.
RotJ Boba gloves are a light grey color with white patches on the fingers and back of the hand. The handbacks are sized differently on each glove.
Good quality replica Boba Fett boots are actually commercially available!
There's also a tutorial at TK-409's site (link below) for making them yourself.
RotJ Boba also has spats, made from the same general fabric as the pouches on the ammo belt.
The last element of the boots are the spikes. They can be made out of anything from wood and plastic to metal.
Boba wears 2 belts. One is a horse girth belt, the other a vinyl or leather ammo belt.
The girth belt for RotJ is a reddish color, where the ESB version is more of a chocolate brown.
The RotJ ammo belt has 8 pouches with no snaps. The ESB version has 7 pouches, and a couple of them have snap closures.
The belt closes with velcro in the back, but has 6 gold grommets on the back, as though it were designed to lace closed.
The EE-3 rifle from RotJ is still based off of the Webley MK I Flare gun, just like the ESB. But for RotJ the base weapon has been heavily modified:
Gallery of screen used weapons, including the RotJ EE-3
Shown here are two different fan made blasters. The top is a custom build off of a bronze Webley cast. The second is a rubber on made by Sci-Fire:
For more on the bronze buildup see Stormtrooperguy.com
These sites all have great information on building a Fett costume.