i would suggest using web safe colors.

I like soft yellow and soft green, too.

Different colors incite different reactions so depending on what you want to place emphasis on you might want to look up color reaction charts before deciding. Light green for example creates a different feeling than light red, both have their uses.

After that its good ol' trial and error until you're happy with the results (try light gray too, it's not on those charts)

try some of the online color wheels, with the tetrad color matching (4 complementary colors) some of them also give gradients and proper gradient stop hex codes, very useful for getting harmonious color schemes - as JS Harris says it's subtle but reactions to unharmonius color schemes can affect eyetracking, depending on the info you're trying to convey

not sure if this link will be allowed but here's one [yafla.com] of the nicer ones I've found for playing around with as it use sliders for saturation and value

I'm using #EEEEEE which gives me a soft pastel blue ..... any suggestions will be appreciated.

My first suggestion would be a new monitor, or recalibrate the one you have. Note that EEEEEE is an equal balance of R = EE, G = EE, and B = EE - This should give you a neutral without a color cast.

Either that, or as suggested, this is outside web-safe and your browser is rendering the next closes web safe color.

The only time it should look bluish is if it's on a warm (red or orange) background due to the visual effect known as simultaneous contrast in which neutral colors appear to take on a color cast that is the compliment of surrounding colors due to the way the human eye interprets collective colors. An inverse example is a neutral would look warm or reddish if surrounded by blue.

Remember the "green U.S. flag" trick, stare at the flag for 60 seconds, then look at a white surface and you see a red white and blue flag - the effect of simultaneous contrast is a result of the same thing.

If you design by the numbers, such subtle distinctions will be of little consequence, but first you have to have a benchmark for what those colors REALLY are - a color wheel or swash book, as suggested.

Unfortunately if your monitor is going south an online color wheel will still be skewed . . .

So to answer the question . . . for neutrals, any values that are equal in all three colors will be neutral . . . you can experiment with those if you want neutrals.

efefef
f4f4f4
f9f9f9

Generally I just choose out the color in Photoshop . . which is why I'm using "eeeeee" instead of "ee", "efefef" instead of "ef" . . . and yes this does lead to web-unsafe sometimes.