You used only percentages of process Magenta in the color stops of your grads. So, for example, the grad in the leftmost object has five color stops, each being a different process color. To Illustrator, it makes no difference that those five different process colors contain only values of the same single CMYK component (Magenta); to Illustrator, they are five different process colors.
If you had first defined a Global process Swatch containing only 100% Magenta, and then used tints of that Global Swatch in your grads, then you could simply change that Global Swatch to Spot, and then replace that Spot with another (219C), and the grad Swatches and objects using tints of the original Global Swatch would update accordingly.
I'm not defending Illustrator's convoluted color handling, I'm just telling you how it is. Illustrator's Global vs. non-Global color distinction is nonsense. It should be done away with, and all colors defined as Swatches should act as Global.
You don't say what version Illustrator you are using. Assuming CS3 or newer, you can:
1. Add a new Swatch for 219.
2. Select All.
3. Edit>Adjust Colors>Recolor Artwork.
4. Colors popup: 1.
5. DoubleClick the color icon under the New column.
6. In the resulting Color Picker, click the Swatches button.
7. In the resulting Swatches list, click the Swatch for 219.
8. Click OK and close the Live Color dialog.
Now if you select one of the grad-filled objects, and click one of its color stops in the Gradient palette, you'll see by looking in the Color palette (Adobe, can we please have a few more different places to look to perform one simple operation?) that the color stop is now a tint of the spot color 219.
Thanks for the reply first...
I tried with your guidance, but some where i am missing. I am not getting spot persentage. If I replace with 219 PMS also in gradient showing Magenta persentage. So kindly explain more detaily and if possible please give that file which you trid.