All I remembered was that the colors could be remembered via the "name" Roy G Biv...I let my laptop do the counting. :)

$ echo roygbiv | tr -d "\n" | wc -m
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Or for much nicer perl powered output:

$ echo roygbiv | perl -e '$a=<STDIN>;chomp $a;printf "There are %d col
+ors in the rainbow.\n",length $a'
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