Workings

Hint
Start by looking at where Alex finished, and where the person who wore #3 finished, and then use clue (6).

Answer
Pos Name   Wore    Colour
1   Alex   #2      red
2   Glen   #3      yellow
3   Stevie #1      green
4   Drew   #4      blue

Reasoning
The four colours were: blue, green, red, yellow.
The four contestants were: Alex, Drew, Glen, Stevie.

By (1), Alex was first.
   1   Alex
   2
   3
   4

By (4), the person who was second wore number #3.
   1   Alex
   2          #3
   3
   4

Looking at (6):
 - first place (Alex) can't have worn #1, because, by (3), Stevie wore #1
 - second place wore #3
 - third place can't have worn #3, because it was worn by second place
 - fourth place is the only entrant who could have worn the same number as their final position

Therefore, Stevie finished in third, and Alex wore #2.
   1   Alex   #2
   2          #3
   3   Stevie #1
   4          #4

By (2), Alex wore red. By (3), the person wearing blue was last.
   1   Alex   #2      red
   2          #3
   3   Stevie #1
   4          #4      blue

By (5), yellow beat green.
   1   Alex   #2      red
   2          #3      yellow
   3   Stevie #1      green
   4          #4      blue

By (4), Glen beat Stevie.
   1   Alex   #2      red
   2   Glen   #3      yellow
   3   Stevie #1      green
   4          #4      blue

Leaving Drew in last place.
   1   Alex   #2      red
   2   Glen   #3      yellow
   3   Stevie #1      green
   4   Drew   #4      blue