Pharo Script of the Day: Colorizing nucleotides

Some days ago I experimented a bit to colorize a random DNA sequence given an alphabet and the desired sequence size, with a little help of BioSmalltalk. This is what I've got:

| text attributes |
text := ((BioSequence forAlphabet: BioDNAAlphabet) randomLength: 6000) sequence asText.
attributes := Array new: text size.
1 to: text size do: [ : index |
  attributes at: index put: { 
  (TextColor color: (BioDNAAlphabet colorMap at: (text at: index))) }  ].
text runs: (RunArray newFrom: attributes).
text.

I built a color map for every nucleotide, based on the alphabet size. This is because in biological sequences (proteins, DNA, RNA) you have a different set of letters.

I should say I don't like the final result. Specially the lack of column alignment:

This seems to persist even trying other attributes

| text attributes |
text := ((BioSequence forAlphabet: BioDNAAlphabet) randomLength: 6000) sequence asText.
attributes := Array new: text size.
1 to: text size do: [ : index |
  attributes at: index put: { 
  (TextColor color: (BioDNAAlphabet colorMap at: (text at: index))) .
  (TextKern kern: 4) }  ].
text runs: (RunArray newFrom: attributes).
text. 

Maybe efforts in Bloc would make it easier for aligning text.