How can I suppress part of an external program's prompt when called from powershell?

I have a powershell script that, among other things, sometimes needs to call a third-party application (TPA) to trigger a login prompt. My issue is that TPA's password prompt includes additional warning lines that I don't need cluttering up my UX. I can (and am) passing the username to the application just fine via $TpaParams, but I'd prefer to leave the handling the user's password to the TPA itself.

The password warning comes through through via STDOUT (not STDERR) and this is the same place that the necessary prompt text comes through. If I redirect the whole thing (Out-Null or the like), then the login fails because it couldn't ask for the password.

I am hoping to be able to show the prompt (only) and strip out the warning. Failing that, I'd be just as happy to recolor the warning text (using Write-Host) to dark-gray-on-blue to make it less eye-catching (I already have a number of colors set up in my script for just this purpose).

Additional (potentially helpful?) data:

TpaCmd is a CMD file that contains lots of error checking plus one line of actual code: "%JAVACMD%" -jar "%JARFILE%" %*
I've been unable to find any help with either Java or TPA's author (IBM), either
I do not have the ability to change the JAR file; it has to remain intact.

Can anyone think of a way to do this on the powershell end?

Things I've tried without success:

No redirection

$TpaCmd login $TpaParams

Password not passed [...]  
Password :

Redirect Out/Err Separately
$TpaCmd login $TpaParams 1> $TmpOut 2> $TmpErr

(null output)

$TmpOut contains

Password not passed [...]

$TmpErr contains

tpapp.cmd : java.lang.NullPointerException  
At D:\path\to\powershell\DoStuff.ps1:288 char:3  
+         &  ${TpaCmd} login --verbose ${TpaParams} 1> $TmpOut  
+         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
    + CategoryInfo          : NotSpecified: (java.lang.NullPointerException:String) [], RemoteException  
    + FullyQualifiedErrorId : NativeCommandError  
  
    at com.tpappname.ds.client.DeployCLI.main(DeployCLI.java:246)  
java.lang.NullPointerException

Redirect Out, leave Err
$TpaCmd login $TpaParams 1> $TmpOut
$TmpOut contains

Password not passed as command line property password or set in environment, DS_PASSWORD

NullPointerException error (above) is displayed to the screen

Redirect Err, leave Out
$TpaCmd login $TpaParams 2> $TmpErr

Password not passed [...]  
Password :

$TmpErr is empty

Redirect Everything
$TpaCmd login $TpaParams *> $TmpAll

(null output)

$TmpAll contains both the password warning and the NPE

Password not passed [...]
Retry with --verbose flag for more info.
tpapp.cmd : java.lang.NullPointerException  
    At D:\path\to\powershell\DoStuff.ps1:288 char:3  
    +         &  ${TpaCmd} login --verbose ${TpaParams} 1> $TmpOut  
    +         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
        + CategoryInfo          : NotSpecified: (java.lang.NullPointerException:String) [], RemoteException  
        + FullyQualifiedErrorId : NativeCommandError  
      
        at com.tpappname.ds.client.DeployCLI.main(DeployCLI.java:246)  
    java.lang.NullPointerException

Solution

After doing a bit more research AND using the answers above as inspiration, I've decided to go with this:

$UserEncryptedPassword = Read-Host "Enter login password" -AsSecureString
& $TpaCmd login $TpaParams -password ([Runtime.InteropServices.Marshal]::PtrToStringAuto([Runtime.InteropServices.Marshal]::SecureStringToBSTR(${UserEncryptedPassword})))

Thank you all for your inspiration and assistance!