selecting sequences in VSE via python This script adds an effect color strip in the VSE then adds an image above it.  I want to add a gamma cross strip so I can do a fade in.  The trouble is there doesn't seem to be a way to select sequence strips by name.  It seems odd that there isn't the ability to so something so simple.  Is there a way to do it or some work around?

    import bpy
    import os           
    import operator     



    class CustomPanel(bpy.types.Panel):
        bl_label = "OpenSource::Classicism XL"
        bl_space_type = "SEQUENCE_EDITOR"
        bl_region_type = "UI"
        bl_options = {'DEFAULT_CLOSED'}

        def draw(self, context):
            def add_label():
                row = self.layout.row()
                row.label("Intro Directory")

            def add_import_button():
                col = self.layout.split().column(align = True)
                col.operator("sequencer.add_intro" , text= "Import")



            add_label()

            add_import_button()



    class Add_Intro(bpy.types.Operator):
        bl_idname = "sequencer.add_intro"
        bl_label = "Add Intro"



        def execute(self, context): 


            selection = []

            def add_sequence_to_list():
                selection.append(bpy.context.selected_sequences[0].name)

            def select_strip(x):
                bpy.context.scene.sequence_editor.sequences_all[image_file_list[0]].use_translation = True

            def add_splash_screen():
                start = 1
                end = 90
                channel = 2
                directory = "C:\\Users\\...\\"
                files = [{"name":"your_image.png"}]
                bpy.ops.sequencer.image_strip_add(directory=directory, files=files, frame_start=start, frame_end=end, channel=channel)
                add_sequence_to_list()

            def add_background_color():
                start = 1
                end = 91
                channel = 1

                bpy.ops.sequencer.effect_strip_add(frame_start=start, frame_end=end, channel=channel, type='COLOR')
                add_sequence_to_list()

            def add_fade_in():
                start = 1
                end = 90
                bpy.ops.sequencer.effect_strip_add(frame_start=1, frame_end=90, type='GAMMA_CROSS')




            add_splash_screen()
            add_background_color()
            add_fade_in()



            return {'FINISHED'}


    def register():
        bpy.utils.register_module(__name__)

    def unregister():
        bpy.utils.unregister_module(__name__)

    if __name__ == "__main__":
        register()
Sequences API methods.

Can use API methods of class bpy.types.Sequences, from the instance scene.sequence_editor.sequences to add new strips to the VSE.  As a "rule of thumb" I avoid using operators whenever possible.  Using the API methods can reference the returned strip on creation, eg a new image strip: image_strip = sequences.new_image(...) removing the need to reference the strip by name at all.

Test script, adds an image strip on channel 1, a color strip on channel 2 and a gamma cross effect strip on channel 3.  The color strips color is set to red.  The gamma cross script uses the other two as input.

import bpy

context = bpy.context
scene = context.scene
sed = scene.sequence_editor
sequences = sed.sequences
# add an image strip
filepath = "/home/batfinger/Pictures/BGLTest.png"
frame_start = 1
frame_end = 90
# add an image strip.
image_strip = sequences.new_image("Image", filepath, 1, frame_start)
# give it a duration
image_strip.frame_final_end = frame_end

color_strip = sequences.new_effect("Color", 'COLOR', 2,
       frame_start=frame_start, 
       frame_end=frame_end)

color_strip.color = (1, 0, 0)

gamma_strip = sequences.new_effect("GammaX", 'GAMMA_CROSS', 3,
       frame_start=frame_start, 
       frame_end=frame_end, 
       seq1=color_strip,
       seq2=image_strip)


Can reference a strip by name via sequences[name] I like to use sequences.get(name) as it will return None if a strip of that name does not exist. 

If an image strip with same name is added twice, eg image_strip = sequences.new_image("Image", ...) again,  the new strip will get the suffix "Image.001" naming.  (Using the operator will do same thing, but with filename.) Can be sure of the name of new strip with image_strip.name.

An issue with your q script is what is image_file_list.