pyqgis - refreshLayerSymbology raster layer legend

When I modify raster colors with PyQGIS, the legend in the layout layer is not update (color and value). The function refreshLayerSymbology() in my code don't do the job.

I had try this :

# BBOX
extent = box
# acces données

provider = self.MNT.dataProvider()
stats = provider.bandStatistics(1, QgsRasterBandStats.All, extent, 0)

if (stats.minimumValue < 0):
    min = 0

else:
    min = stats.minimumValue
max = stats.maximumValue
range1 = max - min

add = range1 // 2
interval = min + add

colDic = {'red': '#ff0000', 'yellow': '#ffff00', 'blue': '#0000ff'}

valueList = [min, interval, max]

lst = [QgsColorRampShader.ColorRampItem(valueList[0], QColor(colDic['blue'])),
       QgsColorRampShader.ColorRampItem(valueList[1], QColor(colDic['yellow'])),
       QgsColorRampShader.ColorRampItem(valueList[2], QColor(colDic['red']))]


myRasterShader = QgsRasterShader()
myColorRamp = QgsColorRampShader()

myColorRamp.setColorRampItemList(lst)
myColorRamp.setColorRampType(QgsColorRampShader.INTERPOLATED)
myRasterShader.setRasterShaderFunction(myColorRamp)

myPseudoRenderer = QgsSingleBandPseudoColorRenderer(self.MNT.dataProvider(),
                                                    self.MNT.type(),

                                                    myRasterShader)
# Add
self.MNT.setRenderer(myPseudoRenderer)

# Refresh the canvas and the legend
self.MNT.triggerRepaint()
#self.iface.mapCanvas().refresh()
self.iface.legendInterface().refreshLayerSymbology(self.MNT)

However when I use the function refreshLayerSymbology() with grayscale color, the function work.

The code I used is :

myGrayRenderer = QgsSingleBandGrayRenderer(self.MNT.dataProvider(), 1)

self.MNT.setRenderer(myGrayRenderer)

renderer = self.MNT.renderer()
# acces données
provider = self.MNT.dataProvider()


layer_extent = self.MNT.extent()
uses_band = renderer.usesBands()

myType = renderer.dataType(uses_band[0])

stats = provider.bandStatistics(uses_band[0],
                                QgsRasterBandStats.All,
                                layer_extent,
                                0)


myEnhancement = QgsContrastEnhancement(myType)
contrast_enhancement = QgsContrastEnhancement.StretchToMinimumMaximum

myEnhancement.setContrastEnhancementAlgorithm(contrast_enhancement, True)
myEnhancement.setMinimumValue(stats.minimumValue)
myEnhancement.setMaximumValue(stats.maximumValue)

self.MNT.renderer().setContrastEnhancement(myEnhancement)

# Refresh the canvas and the legend

self.MNT.triggerRepaint()
self.iface.legendInterface().refreshLayerSymbology(self.MNT)