L3: change ping360 overlay color according to pallete

[jaxxzer]

In some colour palettes the graticule and measuring stick are obscured or difficult to see, it would be preferable to use a contrasting colour to the palette base colour for any overlays.

[patrickelectric]

The user is free to create the pallets himself. The documentation is here: https://docs.bluerobotics.com/ping-viewer/display-settings/#custom-gradients

[jaxxzer]

The problem is that the graduations are not changed according to the pallet. We should add graduation color to the palette definition, or change it automatically somehow to have good contrast with the pallet.

@rjehangir mentioned the same problem