I also thought of painting in joyful lilac.Would that be nice for entire room?

Possibly, if you want a pink room with a slight lilac tinge.

Can you suggest a contrast colour for this room's Master bath?i'm thinking tranquil aqua.

Tranquil Aqua is way too dark and I would not use it as a contrast color in the master bath.
More frequently I paint the master bath the same color as the master bedroom, or a shade lighter. I suggest white walls in the bathroom with lilac or pink towels if you want to continue your pink/lilac color scheme from the master bedroom.

Why do you want to use aqua in the bathroom? Are you using some aqua in the master bedroom?

I'm not planning to use aqua in bedroom, but i just thought the blue would fit well for bath theme.I actually plan to use white decor, curtains and continúe It in the Master bath using white vases, towels etc. But as you suggested using white walls n lilac towels, i like that too.

It is nice to use in the smaller areas, I like the colour, but I think you should use more neutral colour.

A silver/gray on the other walls might calm the Wisteria if you keep it as an accent wall

I like to coordinate the master bedroom and bath, repeating it the colors of one in the other. So having pink/lilac walls in the bedroom with white accents and then white walls in the bathroom with pink/lilac accents would work well. Or the pale pink/lilac walls in both areas with white accents also works.

Go to the dollar store or craft store and buy some white tag or poster board and then invest in some sample colors you think you might like. Paint the boards and move them around the room to see what you like best. I always do this, and good thing! I have about 10 different samples of "white" all over the place right now. I really thought I wanted SW Rice Grain, but when I did the sample board it almost matches my current color. Ugh! I moved lighter to SW Nacre and I think that's what I'm going to go with. . .maybe. You just don't know about a paint color until you get a decent size sample in the space.

Also, just something to think about, I think it's much easier to go with a more neutral paint color and bring color in with accessories. In a few years it will be much easier to change out lilac towels and bedding for something completely different than to repaint.

Personally I think once you have added bed, pictures, side tables and other furnishings, this could look lovely. It all depends what it is going with. What type of furniture and furnishings do you have? Perhaps introduce some taupe or stone colours to soften the white and lilac

Unless you accent the dramatic color with lighter colors and maybe images with a nice matte frame it is too dark of a color.

I like it -- but I would put in lots of white (bedding, gauzy airy white curtains, and accent with silver accents like lighting fixture and lamps). Just my opinion, but the color will look better when you get furniture and accents in there. I would have chosen the Inspired Lilac Carolyn suggested, but I do think this could work with the white and silver accents. I applaud your brave choice of color. Also add artwork with large white mats. Just my opinion....

I think a darker purple would look great! I would think that using the paint for an accent wall may look better in my opinion compared to all of the walls being that purple.