Fix ROI Colour Clash

Rename random generator to be more descriptive as colours selected are not random, update tests to reflect method name change, move secon colour in pallet to another location in pallet to avoid colour clash of ROIs when one ROI is added after another

mantidimaging/gui/windows/spectrum_viewer/spectrum_widget.py

@@ -114,16 +114,16 @@ def get_tof_range(self) -> tuple[int, int]:
         r_min, r_max = self.range_control.getRegion()
         return int(r_min), int(r_max)
 
-    def random_colour_generator(self) -> tuple[int, int, int, int]:
+    def colour_generator(self) -> tuple[int, int, int, int]:
         """
         A random colour generator to colour ROIs boarders.
         Generates colours that are easy to see for colour blind people if colour_blind_friendly is True.
         By default colour_blind_friendly is set to False
 
         @return: A random colour in RGBA format. (0-255, 0-255, 0-255, 0-255)
         """
-        accessible_colours = [(255, 194, 10), (12, 123, 220), (153, 79, 0), (64, 176, 166), (230, 97, 0), (93, 58, 155),
-                              (26, 255, 26), (254, 254, 98), (211, 95, 183), (220, 50, 43)]
+        accessible_colours = [(255, 194, 10), (153, 79, 0), (64, 176, 166), (230, 97, 0), (93, 58, 155), (26, 255, 26),
+                              (12, 123, 220), (254, 254, 98), (211, 95, 183), (220, 50, 43)]
         if self.colour_index == len(accessible_colours):
             self.colour_index = 0
         colour = accessible_colours[self.colour_index]
@@ -175,7 +175,7 @@ def add_roi(self, roi: SensibleROI, name: str) -> None:
         @param name: The name of the ROI.
         """
         roi_object = SpectrumROI(name, roi, pos=(0, 0), rotatable=False, scaleSnap=True, translateSnap=True)
-        roi_object.colour = self.random_colour_generator()
+        roi_object.colour = self.colour_generator()
 
         self.roi_dict[name] = roi_object.roi
         self.max_roi_size = roi_object.size()

mantidimaging/gui/windows/spectrum_viewer/test/spectrum_test.py

@@ -33,15 +33,15 @@ def tearDown(self):
         del self.spectrum_widget
 
     def test_WHEN_colour_generator_called_THEN_return_value_of_length_3(self):
-        colour = self.spectrum_widget.random_colour_generator()
+        colour = self.spectrum_widget.colour_generator()
         self.assertEqual(len(colour), 4)
 
     def test_WHEN_colour_generator_called_THEN_valid_rgb_tuple_returned(self):
-        colour = self.spectrum_widget.random_colour_generator()
+        colour = self.spectrum_widget.colour_generator()
         self.assertTrue(all(0 <= c <= 255 for c in colour))
 
     def test_WHEN_colour_generator_called_THEN_different_colours_returned(self):
-        colour_list = [self.spectrum_widget.random_colour_generator() for _ in range(10)]
+        colour_list = [self.spectrum_widget.colour_generator() for _ in range(10)]
         self.assertEqual(len(colour_list), len({tuple(c) for c in colour_list}))
 
     def test_WHEN_change_roi_colour_called_THEN_roi_colour_changed(self):