Color each individual column in vega

Hi Vega experts, i need help on coloring my Vega Chart, i have a chart with multi series duration and i want to give each column a different color, i mean for example start1 to end1 color blue, start2 to end2 color red and so on....
below is my code.

{
  $schema: https://vega.github.io/schema/vega-lite/v4.json
  description: A simple bar chart with ranged data (aka Gantt Chart).
  data: {
    values: [
      {
        _source: {
          Date: 06-01-2021
          Start1: 00:00
          End1: 00:02
          Start2: 02:46
          End2: 03:47
          Start3: 03:53
          End3: 04:17
          Start4: 04:27
          End4: 04:42
          Start5: 05:06
          End5: 05:25
          Start6: 05:50
          End6: 06:10
          Start7: 06:13
          End7: 06:44
          Start8: 06:52
          End8: 07:14
          Start9: 07:36
          End9: 08:08
          Start10: 11:03
          End10: 15:29
        }
      }
      {
        _source: {
          Date: 07-01-2021
          Start1: 00:00
          End1: 00:12
          Start2: 01:47
          End2: 03:48
          Start3: 03:56
          End3: 04:17
          Start4: 04:29
          End4: 04:57
          Start5: 05:04
          End5: 05:39
          Start6: 05:58
          End6: 06:01
          Start7: 06:23
          End7: 06:32
          Start8: 07:03
          End8: 07:14
          Start9: 07:39
          End9: 07:57
          Start10: 09:00
          End10: 15:38
        }
      }
      {
        _source: {
          Date: 08-01-2021
          Start1: 00:00
          End1: 00:32
          Start2: 02:18
          End2: 03:41
          Start3: 03:57
          End3: 04:03
          Start4: 04:31
          End4: 04:48
          Start5: 05:16
          End5: 05:28
          Start6: 05:56
          End6: 06:00
          Start7: 06:13
          End7: 06:32
          Start8: 06:49
          End8: 07:29
          Start9: 07:45
          End9: 07:54
          Start10: 08:49
          End10: 15:49
        }
      }
    ]
  }
  transform: [
    {
      fold: [
        _source.Start1
        _source.Start2
        _source.Start3
        _source.Start4
        _source.Start5
        _source.Start6
        _source.Start7
        _source.Start8
        _source.Start9
        _source.Start10
      ]
    }
    {
      calculate: datum.key === '_source.Start1' ? datum._source.End1 : datum.key === '_source.Start2'? datum._source.End2: datum.key === '_source.Start3'? datum._source.End3  : datum.key === '_source.Start4'? datum._source.End4 : datum.key === '_source.Start5'? datum._source.End5 : datum.key === '_source.Start6'? datum._source.End6 : datum.key === '_source.Start7'? datum._source.End7 :datum.key === '_source.Start8'? datum._source.End8 :datum.key === '_source.Start9'? datum._source.End9 :datum.key === '_source.Start10'? datum._source.End10 : '00:00'
      as: endValue
    }
  ]
  mark: bar
  encoding: {
    y: {
      field: _source.Date
      type: nominal
      axis: {
        title: Date
      }
    }
    x: {
      field: value
      type: ordinal
      axis: {
        title: Time
      }
    }
    x2: {
      field: endValue
      type: ordinal
    }
  }
  color: {
    field: key
    type: nominal
  }
}

@bab this looks like your color section is not part of your encoding section. If you move color inside encoding then it works the way you expect.