Breath weapon DC = 10 + half lvl + con (or cha for undead).
Dmg is 1 DD per HD + con.
Burst is half the range of a cone, which is half the range of a line.
Lines use d8’s, cones d6’s and burst d4’s as DD.
One stage of a dragon is equal to three character levels, starting at third at wyrmling.
The range for a character goes up each three character levels, with breath weapons being available from third level. So 30 ft. line at lvl 3, 40 ft. at lvl 6, and 60 ft. at lvl 9 etc.
The effects of a breath weapon only affect people that get damaged by the attack.
Black
Line. Methane mist
Highly flammable.
Cone. Paralyzing mist
If you fail a second fortitude save you fall unconscious. If succeeded, make the safe again next turn, with a DC 5 higher. You can't make any saves to wake up, until you're out of the mist.
Burst. Shadow mist
Deals 1d6 shadow damage every turn to everyone in it. Only people with a good aura are immune to this.
Red
Line. Magnesium fire
Times 1.5 damage on people wearing non-metal armor
Cone. Propane fire
Knock enemies back 5 ft. + 5 ft. per size category smaller than the dragon + 5 ft. per 5 failed on the fort save
Burst. Kerosene fire
Set targets hit on fire for 1d3 dmg/round
Orange
Line. Lava blast
Cone. Rocks
Target is confused
Burst. Hot sand
If hit, knocked prone, str save to break free
Yellow
Line. Ice spears
Targets hit get disarmed, their weapon will fall into a random square within 5 feet range
Cone. Hail
Inflict 2 bleed damage per turn
Burst. Cold breath
Targets are frozen in place
Green
Line. Acidic
Non-magical armor of the target gets the broken property, if it's already got the broken property, it breaks and becomes useless
Cone. Adhesive
Target is grappled to the floor, anything he touches sticks to him, str save to break free from a single object stuck. Lasts 10 minutes
Burst. Venomous
Poisoned for 1d3 dmg per turn
Blue
Line. Water spout
Targets are his back 15 feet and knocked prone
Cone. Sonic
Targets hit are deafened and disoriented or stunned (user's choice)
Burst.
Purple
Line. Acetelyne blast
Cone. Lightning
Times 1.5 damage on people wearing metal armor
Burst. Bio shock
Times 1.5 damage on beings made of flesh
White
Ethane Expectorant