If you aren't painting the furniture or the walls, what are you painting?

Some paint companies will tint spray paint to your specification, but if you do that you might as well buy a gallon of paint and a brush. Your main options when it comes to red and yellow spray paint are going to be schoolbus yellow and fire hydrant red then maybe brick red or burgundy. If those aren't the colors your'e going for (and I honestly don't think they would work here anyway) you should look into which companies will tint spray paint and whether you're just better off getting a gallon of paint and a brush or roller.

Here is a good inspiration photo which looks more elegant than childish: http://theprojectlab.blogspot.com/2011/02/nursery.html

A few things you can choose in your bold colors to make the room match your tastes:
- Solid colored lamp, chair, bookshelf, or night stand
- Artwork or typography in your colors
- Or small accent pieces a vase, colored pictures frames etc.

Rustoleum has a Colonial Red that is a little darker red with a blue undertone, instead of orange undertones, that comes in spray cans and pints/quarts for brush painting. http://www.rustoleum.com/CBGProduct.asp?pid=1&sid=7925830

I think by 'primary color' you mean 'really bright color', since chartreuse/mustardy yellow is not a primary color and you seem not to want primary red. Using complex colors like mustard and burgundy is one way to stay sophisticated. A simple way of thinking about how to use colors is the 70-20-10 rule. 70% of the room in your neutrals (which you've got covered by bed, walls, linens) 20% in one accent color and 10% in another accent color. In addition, it's often nice to have one item - like art or a coverlet - with a mixtures of colors you want. I think the chartreuse or a bright citrus yellow-green could work and would be nice with a warm orangey red or with a burgundy.

A place to get wonderful spray colors is a store that caters to street/ graffiti artists. Check out places in your city or onlline. Here's one resource (which I have not used, but have heard they have good colors)

http://www.artsupply.com/montana-spray-paint

.. or just make your own spray paint.

http://hackaday.com/2011/12/01/make-your-own-spray-paint-cans/

You can also try specialty art stores such as Dick Blick's or Prism Art Supplies for unique shades of spray paint. These products are considered high-end and will cost more than something at the home depot, but the quality and color selection are well worth it.

Mustard yellow is also a really popular color for the spring and fall. A lot of big box stores might have a variety of affordable options in shades you are looking for, and discount stores such as TJ Maxx and Marshals will be getting in other stores' 'spring" lines which are also likely to have some muted yellows. My favorite place to look is always the thrift store because you never know what you can find, and low-cost pieces frees you from the guilt of any early spray painting mess-ups.

Primary colors that aren't childish? Why not do something Piet Mondrian inspired. Hey, I found this Mondrian inspired space right here at AT:

http://www.apartmenttherapy.com/from-readers-maudes-mondrian-k-69304

How about something like this? You already have the blue piece on your bed, you could just add in some white/neutral pillows, maybe a green small print pillow (s). I think your bed could be set off by a white lamp and a red throw, as in the picture. It might be fun to play with different patterns, since your current comfortor is so bold and already has a nice pattern to it. Of course, be careful not to overuse the patterns, as this is your retreat from the hectic world. I think a dark-colored catch-all basket placed near the bed could tie in the headboard color nicely, as well.

http://www.bhg.com/decorating/color/paint/green-home-decorating-ideas/#page=10

Anything too matchy-matchy is the worst anyway. Could you decorate with throw pillows and artwork? Based on your bedding chartreuse could work, you can find that and other yellows in pillow covers. It doesn't all need to be the same yellow. I know west elm has a chartreuse tray if you have a nightstand. Another color that would probably look awesome with that bedding (but maybe not in addition to the yellow) is a bright red/orange coral. If you have space for a rug, there's another opportunity to bring in color.

If you do an orange or a reddish-orange, you might be able to counter the primary color feeling. I don't know that you could do anything too bold with that bedding set without it looking a little weird, so make sure all your shades are toned down a bit.

Choose one primary colour as an accent.

If you want to do a mature, stylish red-yellow-blue combo (in any hue) then you should look to the Bauhaus for inspiration, obviously! Just spend an hour doing google searches and you'll easily find tons of images/ info on this design movement. It will complement your furniture and white walls too. Go bold, graphic, minimalist, and functional...

One tip would be to use one primary in its pure state and use muted shades of the other two. You have blue already so maybe lemon and brick?

Oh and use lots of white. Look up Raina and Robert's Farmhouse makeover for some inspiration:)

I agree with Skidou and Seanvick about picking one primary, but not in its purest form because yellow is a KPOW! color and might interfere with your efforts to relax in your space. However, to work with that gray patterned bedspread (it looks gray to me, though some have described it as blue) , I would constrain myself to the mustard yellow, gray, black/brown and perhaps a touch of pumpkin. Check out this beautiful color palette:

http://nauticalcottageblog.com/2011/10/autumn-chills-color-palette-inspires-room-designs/.

Google “yellow and gray bedrooms” for inspiration – it’s a very fresh color combo. The “yellow” includes mustard.

Solid mustard yellow THROW for your bed. A few PILLOWS:

http://www.etsy.com/search?q=yellow%20gray%20pillow&view_type=gallery&ship_to=ZZ&min=0&max=0

RUG: Let’s not forget about your floor. Keep the pattern simple so it doesn’t compete with your bedding.

WALLS/LAMPSHADES: These are the ‘vertical’ opportunities in your room (as opposed to your bed and floor which are ‘horizontal’). You can frame anything (fabric, wallpaper, etc.) to make art.

Hope these ideas get your creative juices going. Good luck with making yourself a cozy nest!

Your room looks good, how about just adding one hot pink pillow on the bed. Go slow.

I like the primary colors in this pic, and they seem similar to the ones you're describing.
http://i224.photobucket.com/albums/dd246/jkomenda/album%202/DSC_0028-1.jpg

Rustoleum makes a lot of yummy paprika-ish reds!

I also suggest getting to an Art Supply store nearby (not craft store). Utrecht, Dick Blick, Pearl, Artist & Craftsman should all have lines of fancy spraypaint in wonderful colors. Their paints are more expensive per can, but well worth it in vibrancy and range. Good luck!