Historical clue formulations

• Deep blue — 2018-10-19
• Shade of blue — 2018-02-25
• Permanent magnet metal — 2017-02-04
• Shade of blue — 2015-03-10
• Discontinued Chevrolet model — 2011-03-09
• Metal that gave its name to a shade of blue — 2009-04-13
• Element in magnetic alloys — 2005-12-18
• Metal found in meteors — 1997-10-19
• Shade of blue — 1996-07-18