app.py

import gradio as gr

custom_css = """
.csbar textarea { overflow-y: scroll; scrollbar-width: thin; scrollbar-color:blue; background-color: red; max-height: 200px; !important }
.csbar textarea::-webkit-scrollbar { display:block; overflow:auto; width:10px; height:10px; background-color:blue; !important }
.csbar textarea::-webkit-scrollbar-track { background: orange; !important }
"""
def plex(moo):
    return "hi"+moo
textbox = gr.Textbox(elem_classes="csbar")

iface = gr.Interface(fn=plex,inputs=textbox,outputs="text",css=custom_css)
iface.launch()