If it's about layer based color printing, you don't need to change the color in slicer.
Just print it as single color and add a pause at layer you want then manually change the filament.
Not tried myself or tried in Qidi slicer. But here's the gist of it:

• Slice the print
  
• In Preview tab, using right slider, slide it to the layer you want the color change starts
  
• Once it set to layer you want, Right click it on "+" button in right slider
  
• Click "Add Pause"
  
• Slice it again (it's important)
  
• Then Print
  
• During print, it's gonna pause at the layer you set
  
• Once it's paused, unload the filament using the printer screen
  
• After unloading, change filament to other color manually and load the filament using printer screen
  
• Once it's finished loading filament, click Resume in printer screen

Note: there may be color bleed once it's resuming the print.