ultima_online is incorrect
1. Yes, both Smith & Tailors start getting colored BODs and Large BODs at 70 (NOT 80).
2. Both skills' BODs are supposed to go from 50% normal/exceptional to 40% normal/60% exceptional at Grandmaster - but this may have changed deliberately or accidently at some point. Recent tests indicate 50/50 spread for 120 Smiths - and a 67-70% normal / 30-33% exceptional split for 120 Tailors!
3. Tailors get no other bonuses.
4. Smiths, and ONLY smiths, get increases in colored BODs at 110 & 120 skill, as of the changes in February 2008. Regardless of skill level, 50% of a smith's BODs will be weapons - as for the other 50%, they are as follows.
70-109.9 Smith skill: 25% Iron Armor, 25% Colored Armor.
110.0-119.9 Smith skill: 15% Iron Armor, 35% Colored Armor.
120 Smith skill: 5% Iron Armor, 45% Colored Armor.