color palette malfunction

[coelacanth]

hi in my gimp color palette a triangle appeared, months ago, in the corners of the color rectangles. i do not know how or why. it sometimes makes it impossible to do what i want to do and sometimes things seem to work normally.
can someone tell me why it appeared? what it is and how to get rid of it? ...and why colors appear there that i haven't chosen for anything?
i've clicked every icon within the color box and many things elsewhere on the page; i've tried the "help" option and i've websearched the question, phrased different ways. i've gotten no explanations and nothing that references it.

...it seems to me one effect it has is it mixes the color i've chosen with the color in the triangle (image 3)...?
another thing that i think is related is that, as my last attached image shows, i try to lighten a color, the triangles disappear (on the palette only, not on the work page) but when i try to use the new color it does not work. (ie, bucket fill - the color stays the darker one... but if i go to a much lighter shade, it seems to mix with the color in the tiangle, making a completely different color - as in image 3)

 Thank you!

[carmen]

The magenta triangle appears in 'LCh mode' (Gimp´s new default--inescapable) to show 'color out of gamut'--maybe very important for some, but I always disregard it.
Look at the top right of your last image: clicking HSV instead makes the triangles disappear.

[Ofnuts]

The purple corners (and purple range in the sliders) correspond to colors that aren't available in your image.

• In full RGB there are colors that cannot be encoded as RGB colors (C<0% or C>100%).
  
• In grayscale these are non-neutral colors
  
• In color-indexed these are colors that are not in the colormap