The 1891 census has Agnes & Robert Christian:

Name Relation Condition Se x Age BirthYear Occupation Where Born
CHRISTIAN, Robert Head Married M 65 1826 Labourer Miner Michael
CHRISTIAN, Agnes Wife Married F 60 1831 Scotland
RG number:RG12 Piece:4682 Folio:57 Page:7
Enumeration District:6 Ecclesiastical Parish:Foxdale
Civil Parish:Patrick
Address:
Castle Town Road, Patrick German

In 1861:
CHRISTIAN, Robert Head Married M 36 1825 Agricultural Labourer Maughold
CHRISTIAN, Agnes Wife Married F 31 1830 Scotland
CHRISTIAN, Andrew Son M 11 1850 Scholar German
CHRISTIAN, Margaret J Daughter F 8 1853 Scholar German
CHRISTIAN, William Son M 6 1855 Scholar German
CHRISTIAN, Edward H Son M 3 1858 German
CHRISTIAN, Evan Son M 1 1860 German

RG number:RG09 Piece:4420 Folio:20 Page:1
Enumeration District:2 Ecclesiastical Parish:St Johns
Civil Parish:German Municipal Borough:
Address:
Rock Mount, German

So this shows the William who died in Colorado. Is this the William you are looking for?

Sue