How can I apply multiple colors to "Lines" in Windows Command Prompt?

Here is a one way, you'll have to figure out the color refs yourself though, I just added these colors as examples:

@echo off
for /F %%a in ('echo prompt $E ^| cmd') do set "ESC=%%a"
cls
echo(
echo(
echo(
echo                                                                                             %ESC%[90m,,%ESC%[0m
echo                                                %ESC%[91m.g8"""bgd%ESC%[0m                                  %ESC%[90m`7MM%ESC%[0m
echo                                                %ESC%[91m.dP'    `M%ESC%[0m                                    %ESC%[90mMM%ESC%[0m
echo                                                %ESC%[91mdm'      `%ESC%[0m    %ESC%[92m,pW"Wq.    ,pW"Wq.%ESC%[0m    %ESC%[90m.P"Ybmmm  MM   .gP"Ya%ESC%[0m
echo                                                %ESC%[91mMM%ESC%[0m           %ESC%[92m6W'   `Wb  6W'   `Wb%ESC%[0m  %ESC%[90m:MI  I8    MM  ,M'   Yb%ESC%[0m
echo                                                %ESC%[91mMM.   `7MMF'%ESC%[0m %ESC%[92m8M     MB  8M     MB%ESC%[0m   %ESC%[90mWmmmp"    MM  8M""""""%ESC%[0m
echo                                                %ESC%[91m`Mb     MM%ESC%[0m   %ESC%[92mYA.   ,A9  YA.   ,A9%ESC%[0m  %ESC%[90m8M         MM  YM.    .%ESC%[0m
echo                                                %ESC%[91m`"bmmmdPY%ESC%[0m    %ESC%[92m`Ybmd9'    `Ybmd9'%ESC%[0m    %ESC%[90mYMMMMMb .JMML. `Mbmmd'%ESC%[0m
echo                                                                                   %ESC%[90m6'    dP%ESC%[0m
echo                                                                                    %ESC%[90mYbmmmd'%ESC%[0m
echo(
echo(
echo(
pause>nul

Result:

EDIT

Here is a reference to the ansi color escape codes.

Here's a somewhat neater looking version of the windows-10 ANSI escape code method, already suggested by Gerhard.

@Echo Off
SetLocal EnableExtensions
For /F %%G In ('Echo Prompt $E ^| "%__AppDir__%cmd.exe"') Do Set "ESC=%%G"
ClS
Echo=
Echo=
Echo=
Echo                             %ESC%[92m                                                ,,
Echo                             %ESC%[94m  .g8"""bgd  %ESC%[92m                                 `7MM
Echo                             %ESC%[94m .dP'    `M  %ESC%[92m                                   MM
Echo                             %ESC%[94m dm'      `  %ESC%[91m  ,pW"Wq.  %ESC%[93m  ,pW"Wq. %ESC%[94m  .P"Ybmmm %ESC%[92m   MM  %ESC%[91m  .gP"Ya
Echo                             %ESC%[94m MM          %ESC%[91m 6W'   `Wb %ESC%[93m 6W'   `Wb%ESC%[94m :MI  I8   %ESC%[92m   MM  %ESC%[91m ,M'   Yb
Echo                             %ESC%[94m MM.   `7MMF'%ESC%[91m 8M     MB %ESC%[93m 8M     MB%ESC%[94m  Wmmmp"   %ESC%[92m   MM  %ESC%[91m 8M""""""
Echo                             %ESC%[94m `Mb     MM  %ESC%[91m YA.   ,A9 %ESC%[93m YA.   ,A9%ESC%[94m 8M        %ESC%[92m   MM  %ESC%[91m YM.    .
Echo                             %ESC%[94m  `"bmmmdPY  %ESC%[91m  `Ybmd9'  %ESC%[93m  `Ybmd9' %ESC%[94m  YMMMMMb  %ESC%[92m .JMML.%ESC%[91m  `Mbmmd'
Echo                             %ESC%[94m                                   6'    dP
Echo                                                                 Ybmmmd' %ESC%[0m
Echo=
Echo=
Echo=
Pause 1> NUL

You could even mess around with it to put it into a bright white box, for instance:

@Echo Off
SetLocal EnableExtensions
For %%# In (BG FG)Do Set "%%#="
For /F %%# In ('%__AppDir__%WindowsPowerShell\v1.0\powershell.exe -NoP ^
    "$Console=(Get-Host).UI.RawUI;Switch($Console.BackgroundColor," ^
    "$Console.ForegroundColor){'Black'{40}'DarkBlue'{44}'DarkGreen'{42}" ^
    "'DarkCyan'{46}'DarkRed'{41}'DarkMagenta'{45}'DarkYellow'{43}'Gray'{47}" ^
    "'DarkGray'{100}'Blue'{104}'Green'{102}'Cyan'{106}'Red'{101}" ^
    "'Magenta'{105}'Yellow'{103}'White'{107}}" 2^>NUL')Do If Not Defined BG (
    Set "BG=%%#")Else Set "FG=%%#"
For /F %%G In ('Echo Prompt $E ^| "%__AppDir__%cmd.exe"') Do Set "ESC=%%G"
ClS
Echo=
Echo=
Echo=
Echo                             %ESC%[92;107m                                                ,,            %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m  .g8"""bgd  %ESC%[92m                                 `7MM            %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m .dP'    `M  %ESC%[92m                                   MM            %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m dm'      `  %ESC%[91m  ,pW"Wq.  %ESC%[93m  ,pW"Wq. %ESC%[94m  .P"Ybmmm %ESC%[92m   MM  %ESC%[91m  .gP"Ya  %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m MM          %ESC%[91m 6W'   `Wb %ESC%[93m 6W'   `Wb%ESC%[94m :MI  I8   %ESC%[92m   MM  %ESC%[91m ,M'   Yb %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m MM.   `7MMF'%ESC%[91m 8M     MB %ESC%[93m 8M     MB%ESC%[94m  Wmmmp"   %ESC%[92m   MM  %ESC%[91m 8M"""""" %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m `Mb     MM  %ESC%[91m YA.   ,A9 %ESC%[93m YA.   ,A9%ESC%[94m 8M        %ESC%[92m   MM  %ESC%[91m YM.    . %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m  `"bmmmdPY  %ESC%[91m  `Ybmd9'  %ESC%[93m  `Ybmd9' %ESC%[94m  YMMMMMb  %ESC%[92m .JMML.%ESC%[91m  `Mbmmd' %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m                                   6'    dP                   %ESC%[%FG%;%BG%m
Echo                             %ESC%[94;107m                                    Ybmmmd'                   %ESC%[%FG%;%BG%m
Echo=
Echo=
Echo=
Pause 1> NUL
GoTo :EOF

This above method leverages powershell to determine, and create variables using the current console foreground and background colors. This ensures that they are reset correctly after the color changed image lines have been processed. (Of course the script writer could just define known colors, right from the outset)

I will add however, that the command line is supposed to be for typing commands and reading text output, not for displaying unnecessary childish images and colors. If you want a GUI, build a GUI program, not a console one.