How to slowly turn text to another color?

Question

I want to make my red text slowly turn to green (and later to blue). Of course I was traying to make it by myself. Here's the code where I was traying for start turn slowly color from black to red:

from guizero import App, Text
from time import sleep

done = 0
re = 0
ge = 0
be = 0

app = App("My title")
a  = Text(app, text="Hello World", color = "black")

while done == 0:
    a.text_color = (re, ge, be)
    re = re + 1
    if re == 256:
        done = 1
    sleep(0.1)

app.display()

Then when I'm turning on the code I see no error and app, IS on the screen, but it can't show any text and it's crushing (after some time I see "(not responding)" on the top of the app... and that's it!). I'm always see no error.

If it can help I'm working on mu.

I was traying:

• diffriend way to make code delaying
• put while command in the def loop
• adding glabal command
• combining these ideas

I can't fix it! Can someone help?

Please!

There is more data. By your commants I did new code where I started to do it fully (to first turn from red to green, later to blue and to again red) (there's again the same not responding problem):

from guizero import App, Text,PushButton
from time import sleep

re = 255
ge = 0
be = 0

don = 0
work = 1

def strt():
    global don, re, ge, be, work
    start.hide()
    seco.show()
    for x in range(2):
        don = 0
        while don == 0:
            if work == 1:
                if not re == 0:
                    re = re - 1
                    ge = ge + 1
                else:
                    work = 2
            elif work == 2:
                if not ge == 0:
                    ge = ge - 1
                    be = be + 1
                else:
                    work = 3
            elif work == 3:
                if not be == 0:
                    be = be - 1
                    re = re + 1
                else:
                    work = 1
                    don = 1
            seco.text_color = (re, ge, be)
            sleep(0.1)

app = App("Top Secret (yet)")
app.bg = "black"
fill = Text(app, "", 200)
start = PushButton(app, strt, text="Start!")
start.bg = "blue"
seco = Text(app, "nothing", 50, color = (re,ge,be), font = "Algerian")
seco.hide()

app.display()