Here's a variation on one of my favorite classic cocktails, the Aviation, with an appropriate color adjustment. Time to break out some very precise measurements:
1 1/2 oz London dry gin (I used the wonderful Boodles, which first got me hooked on gin)
2/3 oz maraschino liqueur (always Luxardo)
1/4 oz Campari (or Aperol)
1/4 oz lemon juice
1/4 oz orange juice (just to round the acidity off a little)
Shake and strain into a cocktail glass, then garnish with a maraschino cherry dropped right into the center.