Грокаем Spans.

SpannableString spannableString = new SpannableString("abcd");
BackgroundColorSpan backgroundSpan = new BackgroundColorSpan(Color.RED);
spannableString.setSpan(backgroundSpan, 1 /* start */, 3 /* end */, Spannable.EXCLUSIVE_EXCLUSIVE);
textView.setText(spannableString);

SpannableStringBuilder spannableString = new SpannableStringBuilder("abcd");
BackgroundColorSpan backgroundColorSpan = new BackgroundColorSpan(Color.RED);
spannableString.setSpan(backgroundColorSpan, 1, 3, flag);
spannableString.insert(3, "x");
spannableString.insert(1, "x");

/*
public BulletSpan (int gapWidth, int color)
-gapWidth: gap in px between bullet and text
-color: bullet color (optionnal, default is transparent)
*/

// create a cyan BulletSpan with a gap of 8dp
// note: toPx - converts dp to pixels
span = new BulletSpan(toPx(8), Color.CYAN);

/*
public QuoteSpan (int color)
-color: quote vertical line color (optionnal, default is Color.BLUE)
*/

// create a cyan quote
span = new QuoteSpan(Color.CYAN);

/*
public Standard(Layout.Alignment align)
-align: alignment to set
*/

// align center a paragraph
span = new AlignmentSpan.Standard(Layout.Alignment.ALIGN_OPPOSITE);

// underline a character
span = new UnderlineSpan();

// strikethrough a character
span = new StrikethroughSpan();

// subscript a character
span = new SubscriptSpan();

// superscript a character
span = new SuperscriptSpan();

/*
public BackgroundColorSpan (int color)
-color: background color
*/

// set a cyan background
span = new BackgroundColorSpan(Color.CYAN);

/*
public ForegroundColorSpan (int color)
-color: foreground color
*/

// set a cyan foreground
span = new ForegroundColorSpan(Color.CYAN);

//replace a character by cat image
span = new ImageSpan(getApplicationContext(), R.drawable.cat);

/*
public StyleSpan (int style)
-style: int describing the style (android.graphics.Typeface)
*/

// set a bold style
span = new StyleSpan(Typeface.BOLD);

/*
public TypefaceSpan (String family)
-family: a font family
*/

// set the serif family
span = new TypefaceSpan("serif");

/*
public  TextAppearanceSpan(Context context, int appearance, int colorList)
-context: a valid context
-appearance: text appearance resource (ex: android.R.style.TextAppearance_Small)
-colorList: a text color resource (ex: android.R.styleable.Theme_textColorPrimary)

public TextAppearanceSpan(String family, int style, int size, ColorStateList color, ColorStateList linkColor)
-family: a font family
-style: int describing the style (android.graphics.Typeface)
-size: text size
-color: a text color
-linkColor: a link text color
*/

//set the serif family
span = new TextAppearanceSpan(this/*a context*/, R.style.SpecialTextAppearance);

/*
public AbsoluteSizeSpan(int size, boolean dip)
-size: a size
-dip: false, size is in px; true, size is in dip (optionnal, default false)
*/

// set text size to 8dp
span = new new AbsoluteSizeSpan(toPx(8));

/*
public RelativeSizeSpan(float proportion)
-proportion: a proportion of the actual text size
*/

// set text size 2 times bigger 
span = new RelativeSizeSpan(2.0f);

/*
public ScaleXSpan(float proportion)
-proportion: a proportion of actual text scale x
*/

//scale x 2 times bigger 
span = new ScaleXSpan(2.0f);

/*
public MaskFilterSpan(MaskFilter filter)
-filter: a filter to apply
*/

// blur a character
span = new MaskFilterSpan(new BlurMaskFilter(toPx(4), BlurMaskFilter.Blur.NORMAL));
// emboss a character
span = new MaskFilterSpan(new EmbossMaskFilter(new float[] { 1, 1, 1 }, 0.4f, 6, 3.5f));

public class FrameSpan extends ReplacementSpan {

    private int width;

    @Override
    public int getSize(@NonNull Paint paint, CharSequence text, int start, int end, @Nullable Paint.FontMetricsInt fm) {
        return  (int) paint.measureText(text, start, end);
    }

    @Override
    public void draw(@NonNull Canvas canvas, CharSequence text, int start, int end, float x, int top, int y, int bottom, @NonNull Paint paint) {
        int color = paint.getColor();
        paint.setColor(Color.YELLOW);
        width = (int) paint.measureText(text, start, end);
        canvas.drawRect(x, top, x + width, bottom, paint);
        paint.setColor(color);
    }
}

public class RoundBackgroundSpan implements LineBackgroundSpan {

    private final int padding = 0;
    private final RectF backgroundRect = new RectF();

    @Override
    public void drawBackground(Canvas c,
                               Paint p,
                               int left,
                               int right,
                               int top,
                               int baseline,
                               int bottom,
                               CharSequence text,
                               int start, int end, int lnum) {
        if(text == null) return;
        int textWidth = Math.round(p.measureText(text, start, end));
        int paintColor = p.getColor();
        backgroundRect.set(left - padding, top - lnum == 0 ?  padding / 2  :  -(padding / 2),
        left + textWidth + padding, bottom + (padding / 2));
        p.setColor(Color.CYAN);
        c.drawRoundRect(backgroundRect, toPx(4), toPx(4), p);
        p.setColor(paintColor);
    }
}

public class MutableForegroundColorSpan extends ForegroundColorSpan {

    @ColorInt
    private int foregroundColor;

    public MutableForegroundColorSpan(@ColorInt int color) {
        super(color);
        foregroundColor = color;
    }

    public MutableForegroundColorSpan(Parcel src) {
        super(src);
        foregroundColor = src.readInt();
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        super.writeToParcel(dest, flags);
        dest.writeInt(foregroundColor);
    }

    @Override
    public void updateDrawState(TextPaint ds) {
        ds.setColor(getForegroundColor());
    }

    @Override
    public int getForegroundColor() {
        return foregroundColor;
    }

    public void setForegroundColor(@ColorInt int foregroundColor) {
        this.foregroundColor = foregroundColor;
    }
}

    private final Property<MutableForegroundColorSpan, Integer> MUTABLE_FOREGROUND_COLOR_PROPERTY =
            new Property<MutableForegroundColorSpan, Integer>(Integer.class, "MUTABLE_FOREGROUND_COLOR_PROPERTY") {
                @Override
                public Integer get(MutableForegroundColorSpan object) {
                    return object.getForegroundColor();
                }

                @Override
                public void set(MutableForegroundColorSpan object, Integer value) {
                    object.setForegroundColor(value);
                }
            };

        TextView animatedTextView = new TextView(this);
        addContentView(animatedTextView, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.WRAP_CONTENT));

        SpannableString text = new SpannableString(getString(R.string.text));
        MutableForegroundColorSpan span = new MutableForegroundColorSpan(Color.BLACK);
        text.setSpan(span, 0, text.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        animatedTextView.setText(text);

        ObjectAnimator animator = ObjectAnimator.ofInt(span, MUTABLE_FOREGROUND_COLOR_PROPERTY, Color.BLACK, Color.CYAN, Color.DKGRAY);
        animator.setEvaluator(new ArgbEvaluator());
        animator.addUpdateListener(animation -> {
            animatedTextView.invalidate();
        });
        animator.setDuration(3500L);
        animator.start();