Backcolor's make event text un-readable

Edit: I need to be able to dynamically change colors for multiple events within the same calendar, so i need options to alter the colour itself instead of altering how the text shows up against the color

The backColor property will accept all color formats defined in the CSS spec (it's translated to an inline "background" style):

https://developer.mozilla.org/en-US/docs/Web/CSS/color_value

To specify the color using RGB components, you can use this:

onBeforeEventRender: function(args) {
  args.data.backColor = "rgb(255, 45, 0)";  //   = #FF2D00
}

You can use rgba() to specify transparency (alpha channel):

onBeforeEventRender: function(args) {
  args.data.backColor = "rgb(255, 45, 0, 0.5)";  //   = #FF2D00 with 50% transparency
}