Just so you know, we don't know the file format for every file. If it's just a bunch of random characters, it's probably a .zip or .jar.

# takes in a line of text to colour, a start colour in hex, and an end colour in hex
function gradientText(text: text, start-colour: text, end-colour: text) :: text:
    if "%{_start-colour}%%{_end-colour}%" doesn't match "[0-9a-fA-F]*":
        return "Invalid Colour"
    
    set {_text-length} to length of {_text}
    # get starting rgb values
    set {_red-start} to hexToDecimal(substring of {_start-colour} from 1 to 2)
    set {_green-start} to hexToDecimal(substring of {_start-colour} from 3 to 4)
    set {_blue-start} to hexToDecimal(substring of {_start-colour} from 5 to 6)
    # get ending rgb values
    set {_red-end} to hexToDecimal(substring of {_end-colour} from 1 to 2)
    set {_green-end} to hexToDecimal(substring of {_end-colour} from 3 to 4)
    set {_blue-end} to hexToDecimal(substring of {_end-colour} from 5 to 6)
    # get the amount they should change each character
    set {_red-step} to ({_red-end} - {_red-start}) / {_text-length}
    set {_green-step} to ({_green-end} - {_green-start}) / {_text-length}
    set {_blue-step} to ({_blue-end} - {_blue-start}) / {_text-length}
    debug {_red-start}, {_blue-start}, {_green-start}

    loop {_text-length} times:
        # get rgb values for the current character
        set {_r} to round({_red-start} + ({_red-step} * loop-number))
        set {_g} to round({_green-start} + ({_green-step} * loop-number))
        set {_b} to round({_blue-start} + ({_blue-step} * loop-number))
        # add colour + character to the string
        set {_return-text} to "%{_return-text} ? ""%<##%decimalToHex({_r})%%decimalToHex({_g})%%decimalToHex({_b})%>%character at loop-number of {_text}%"
    # return final string
    return formatted {_return-text}

# decimal to hexadecimal helper function. domain of 0-255.
function decimalToHex(decimal: number) :: text:
    return ("00" if {_decimal} <= 0, else ("FF")) if {_decimal} is not between 0 and 255
    return join (character at (mod((floor({_decimal} / 16)), 16) + 1) in "0123456789ABCDEF") and (character at ((mod({_decimal}, 16)) + 1) in "0123456789ABCDEF")

# hexadecimal to decimal helper function. requires two hex digits, domain of 0-255.
function hexToDecimal(hex: text) :: number:
    return 0 if {_hex} does not match "[0-9a-fA-F]{2}"
    set {_hex} to {_hex} in uppercase
    return 16 * (first index of (character at 1 in {_hex}) in "0123456789ABCDEF" - 1) + (first index of (character at 2 in {_hex}) in "0123456789ABCDEF" - 1)